Glitches killing Gonarch with gas

Trying to beat Gonarch with gas brought through Xen and teleported earlier in the level. After taking the left turn into the tunnel up to where the gas is activated for the final fight, sometimes the gonarch will stop at the entrance and fail to complete its animation and the game can’t proceed. Sometimes it does complete its animation and seal the entrance to the tunnel, but then after activating the gas and killing it, I still won’t be able to jump off the ledge from where that was done, invisible wall is still there.

map : bm_c4a2c at: 1340 x, -117 y, -1466 z
setpos 1340.105957 -117.868530 -1466.557495;setang 8.937875 157.006393 0.000000

These console entries consistently appear in this section when this happens:

Particle system ChaseFired could not find control point entity (ChaseFired38)
Particle system ChaseFired could not find control point entity (ChaseFired39)
main_chase_gonarch: unknown scripted sequence “”