Test case WAD: https://cdn.discordapp.com/attachments/629464748743720975/664337769618997288/MAP01.wad
Ride the rock over the grates until it respawns in the pit (without dismounting), then jump (note: Eldog had trouble reproducing this locally, but it happened without fail in netgames)
Crash report: https://cdn.discordapp.com/attachments/629464748743720975/664337572851482647/srb2win.RPT
Investigating a crash report under identical conditions from a modded EXE seemed to lead to this line being the culprit:
Ride the rock over the grates until it respawns in the pit (without dismounting), then jump (note: Eldog had trouble reproducing this locally, but it happened without fail in netgames)
Crash report: https://cdn.discordapp.com/attachments/629464748743720975/664337572851482647/srb2win.RPT
Investigating a crash report under identical conditions from a modded EXE seemed to lead to this line being the culprit: