diff --git a/Cargo.toml b/Cargo.toml
index 4b9b684..a422c88 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -15,10 +15,10 @@ lazy_static = "1.4"
 clap = { version = "4.1", features = ["derive"] }
 thiserror = "1.0"
 enum-display-derive = "0.1"
-queues = "1.1.0"
-duration-str = { version = "0.5.1", features = ["serde"] }
-signal-hook = "0.3.17"
+queues = "1.1"
+duration-str = { version = "0.5", features = ["serde"] }
+signal-hook = "0.3"
 
 [target.'cfg(target_os = "linux")'.dependencies]
-alsa = "0.7.0"
+alsa = "0.7"
 libc = "0.2.21"
diff --git a/src/eventmap.rs b/src/eventmap.rs
index a2ad23d..b61ef19 100644
--- a/src/eventmap.rs
+++ b/src/eventmap.rs
@@ -44,7 +44,8 @@ impl<'a> EventMap<'a> {
             for ev in v {
                 if ev.match_value(event) {
                     for r in &ev.run {
-                        r.run(event.make_env(ev.remap.as_ref(), ev.float )?.to_map(r.envconf.as_ref()))?;
+                        let env = event.make_env(ev.remap.as_ref(), ev.float )?.to_map(r.envconf.as_ref());
+                        r.run(env)?;
                     }
                 }
             }
diff --git a/src/main.rs b/src/main.rs
index c49fe3c..4650771 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -24,13 +24,16 @@ fn main() {
     loop {
         match run_file(&c.map_file) {
             Ok(_) => (),
-            Err(err) => println!("Error: {}", err)
+            Err(err) => {
+                eprintln!("Error: {}", err);
+                std::process::exit(1);
+            }
         }
     }
 }
 
 fn run_file(filepath: &Path) -> Result<(), Error> {
-    println!("Load file {}", filepath.to_str().unwrap());
+    println!("Load file {}", filepath.to_str().unwrap_or("<unknown>"));
     let dat = std::fs::read( filepath )?;
     let conf = Config::try_from(&dat[..])?;
     run::run_config(&conf)
diff --git a/src/midi/mod.rs b/src/midi/mod.rs
index 411b8b7..6e00571 100644
--- a/src/midi/mod.rs
+++ b/src/midi/mod.rs
@@ -202,6 +202,7 @@ where T: MidiInputHandler + Send
         // parking signal for runner, true = stop
         let (pts,prs) = mpsc::channel::<bool>();
 
+        // event queue populated by the main thread and consumed by the exec thread
         let evq = Arc::new(Mutex::new(CircularBuffer::<EventBuf>::new(conf.queue_length)));
 
         // background execution loop
@@ -222,6 +223,7 @@ where T: MidiInputHandler + Send
                         }
                     };
                     eventmap.run_event(&ev.as_event()).unwrap_or_else(|e| eprintln!("ERROR: error on run: {}", e) );
+                    // wait until interval has been reached
                     let elapsed_time = start.elapsed();
                     if elapsed_time < conf.interval {
                         thread::sleep(conf.interval - elapsed_time);
diff --git a/src/run.rs b/src/run.rs
index 12dabda..cdb3dc4 100644
--- a/src/run.rs
+++ b/src/run.rs
@@ -11,7 +11,7 @@ use crate::config::{Config,DeviceConfig};
 use crate::eventmap::EventMap;
 
 type DeviceRunItem<'a> = (&'a DeviceConfig, EventMap<'a>, Option<Arc<Mutex<(u32, u32)>>>);
-type DeviceRunResult<'a> =(thread::ScopedJoinHandle<'a, ()>, mpsc::Sender<bool>);
+type DeviceRunResult<'a> =(thread::ScopedJoinHandle<'a, Result<(), Error>>, mpsc::Sender<bool>);
 
 pub fn cross_shell(cmd: &str) -> Vec<String> {
     if cfg!(target_os = "windows") {
@@ -54,7 +54,7 @@ pub fn run_config(conf: &Config) -> Result<(), Error> {
     });
 
     thread::scope(|s| -> Result<(), Error> {
-        let mut threads: Vec<(thread::ScopedJoinHandle<'_, ()>, mpsc::Sender<bool>)> = Vec::new();
+        let mut threads: Vec<DeviceRunResult> = Vec::new();
         let ports = input.ports()?;
         for p in ports {
             if let Some(v) = try_connect_process(&input, s, &p, &cfevmap)? { threads.push(v) }
@@ -77,7 +77,7 @@ pub fn run_config(conf: &Config) -> Result<(), Error> {
         event_thread.join().unwrap()?;
         for (thread,ss) in threads {
             let _ = ss.send(true);
-            thread.join().unwrap();
+            let _ = thread.join().unwrap().map_err(|e| eprintln!("WARN: error in thread: {}", e));
         }
         Ok(())
     })?;
@@ -91,29 +91,36 @@ fn try_connect_process<'a>(
     cfevmap: &'a[DeviceRunItem<'a>],
     )
         -> Result<Option<DeviceRunResult<'a>>, Error> {
-    for (dev, eventmap, m) in cfevmap {
-        if let Some(m) = m {
+    for (dev, eventmap, counter) in cfevmap {
+        // device counter is full
+        if let Some(m) = counter {
             let m = m.lock().unwrap();
             if m.0 >= m.1 {
                 continue;
             }
         }
+
         if let Some(mut c) = input.try_connect(p.clone(), PortFilter::from(*dev))? {
-            if let Some(m) = m {
+            // increase device counter
+            if let Some(m) = counter {
                 let mut m = m.lock().unwrap();
                 m.0 += 1;
             }
+            // stop signal channel
             let (sts,srs) = mpsc::channel::<bool>();
+            let mm = counter.as_ref().map(Arc::clone);
             let nsts = sts.clone();
-            let mm = m.as_ref().map(Arc::clone);
-            let t = s.spawn( move || {
-                dev.run_connect().unwrap();
-                c.run(dev, eventmap, (nsts,srs)).unwrap();
+            let t = s.spawn( move || -> Result<(), Error> {
+                dev.run_connect()?;
+                // blocking process
+                c.run(dev, eventmap, (nsts,srs))?;
+                // decrease device counter
                 if let Some(m) = mm {
                     let mut m = m.lock().unwrap();
                     m.0 -= 1;
                 }
-                dev.run_disconnect().unwrap();
+                dev.run_disconnect()?;
+                Ok(())
             });
             return Ok(Some((t, sts)));
         }