Steps to reproduce:
1/ Download "Experimental 17-3.zip" 2/ Sync mods (i found only LTN +opteralib are required.. without them trains would stop)
3/ Open this save
4/ Wait 5s (time required for construction bots to remove some rails and go back into roboports)
5/ Try to save
6/ Crash
Add couple of seconds in step 4 for
crash RailBlock-checkConsistency line 314, +0s in step 4
crash TrainManager-checkConsistency line 981, +10s in step 4
crash RailSignalBase-checkConsistency line 359, -2s in step 4
crash TrainManager-checkConsistency line 984, earliest tick found using editor single tick
---more deterministic reproduction:
1/ Download "Experimental 17-4.zip" 2/ Sync mods
3/ Open save
4/ In editor -> time, press "Tick once"
5/ Try to save
6/ Crash
log
4/ Tick custom -> 300
log