I found this post from several years ago...
This is still a problem for me in v 10.5.1. When setting a track delay on an External MIDI Instrument, it is ignored. I also had trouble getting consistent results with multi-timbral instruments (only most recent value you entered works). The only thing that seems to work is a single Software Instrument track.
I am building a large orchestral template with about 275 tracks. Trying to avoid creating 275 Software Instrument tracks. But maybe that's the right solution... ?
I put together a project that illustrates the problem. The solo Software Instrument track works, but the multi-timbral doesn't. Neither does the MIDI Instrument (Environment) track.
Any help is appreciated.