No portal to the next room in Coward's Trial unique map

I can't proceed in Coward's Trial unique map.

I go to the first room, kill the mobs and then nothing. I see that there are 19 monsters left, but there are none I see (and the first room is quite small).
Tried to portal to my hideout and back - no result. Tried buying another map - same result. Not sure what else to try, and maps are not very cheap - 50c.

As I understand (from watching videos), an arc with a portal to the next room should appear. It's not happening for me.

Not sure if it's relevant, but in case it's an interaction with skills I use - I use Summon Raging Spirit as a main damaging skill. Plus, other summons. (SRS Guardian)

It's the last map for my atlas completion, please help! :)

Tried it again without spectres and on another server (was on Paris, tried on Moscow) - success, no issues at all and all worked fine.