There is possibility that the project got somehow corrupted.
You could try exporting those two tracks (or the MIDI files) and rebuild the project (using a newly created template) after having reset (deleted) Logic's prefs.
LogicPro 10.6.3, MainStage3.5.3
MBPro 17", Core2Duo, 8G, OSX 10.12.6
MacPro, Xeon 6Cores, 64GB, OSX 10.15.7
ULN8, MOTU MIDI TP-AV, C4, MCU Pro, KorgNano, Novation SLMkII
AAS, NI, Celemony, Spectrasonics, Korg, Arturia, etc...
PC, iPadPro 5th gen 12.9”(Duet D., V-Control & LogicRemote), AtariST(Notator SL), Several vintage gear