Midi import problem

[Controller]

1. When using imported Midi files with modified instruments, OpenMPT stops playing sounds after a short while (==).
Does OpenMPT create those == mute instructions when converting because of the default midi instrument length?
My problem is that I want to use custom instruments afterwards, which differ in length.

2. Is there a way to import and use any dls file to the midi library, regardless internal instrument names (dls intrument no.  x gets midi library instrument no. x)? (However, I got lot's of problems even
with the default gm.dls file on my computer