Yes please I’m loosing my mind ! 
An external midi note is sent back just once, they are recorded, not played.
There are more non working notes than I thought on the chromatic keyboard. Did I missed them or it changed ? 
I check notes again and powercycle.
Edit : F2, F#2, G2, G#2, A2
C3, E3, A3, A#3, B3
C4, C#
I used a new project.
Edit I can’t see midi activity pixel on OT when I use these notes with chromatic trigs. I unplugged midi cables…
Ok, I think I understood the weird behavior with notes. It’s my fault : I was sending Notes On only, so notes from external midi, were not sent anymore.
The more you send notes ON, the less you can send !
I think this is problematic if there is a note off error. You can’t send that note anymore, unless you send back the same note off, or power cycle. I changed the project without success. Double stop didn’t change the behavior.
I deleted irrelevant posts.
Back to tests with notes on and off !
have you recreated the scenario I posted originally using the OT’s “keyboard” (Chromatic Mode)
Not yet. I was able to record with chromatic trigs, but the notes on without notes off fucked my tests !
Note : I found an illogical behavior : when you hold a trig to plock external midi notes, LEN and VEL are set only once. If you hold again longer different notes the LEN and VEL remain the same.
Edit :
@marcelvidela I couldn’t replicate, it behaved as intended. Check arp settings, if you’re not transposed, out of range, check midi out activity with the right pixel above Tempo display and also check with a midi monitor if you don’t find.
I’m off ! 
All of a sudden I have this same scenario. It is mind boggling.
I’ve tried with different ext gear and different MIDI cable combos. Yes Everything works on the chromatic mode, yet nothing coming out of the sequencer tracks.
Did you have any luck?
on the OT mixer, instead of solid squares for active tracks, they were dotted empty squares.
MIDI track 8 on the OT mixer had an “S” instead of a square. This track could send MIDI sequences but would not mute.
anyone know what happened?
SOLVED: Change Project.
goodbye project.
REMINDER: Backup your projects
A quick look into the manual (mixer menu section) would give you this:
It is possible to solo tracks by pressing [CUE] + the [TRIG] keys corresponding to the tracks you want to solo. A solo’ed track is indicated by a green [TRIG] key and the letter “S”. Unsolo a track by repeating the key combination. Tracks that will be audible once all tracks are unsolo’ed are indicated by half bright red [TRIG] keys and dotted squares. The [TRIG] keys of tracks muted before the solo operation will be unlit. When exiting the solo mode these tracks will stay muted. Muted tracks being soloed will revert to their muted status once solo mode is exited.
That was it. Thanks. Now I know OT has solo. Did I not read the manual, ffs?