After going through the PC-Steam release of the Halo 4 Reclaimer mission once without issue, re-entering the mission in any difficulty leads to multiple bugs… including:
1a) After 2nd river crossing, the terrain loading failed & became invisible…
1b) A separate time, the Mammoth also became invisible … (neither time would it trigger a mission-progression checkpoint after stopping.
2a) Separately from #1, at the hill where you would normally board the Covenant ship that damaged the mini-mac, I encountered a loop where the Covenant dropships reloaded about 6 times (drop the wraith or ghosts, leave, reset, drop the vehicles again, leave, reset, repeat previous loop about 3x.)
2b) Then, after that loop finished, the boarding ship didn’t load, blocking mission progression.
This mission is very unstable, and it’s not consistently so either.