Frostmourne not summoning killed minions

[Rhasimir-1573]

There are already dozens of threads about that, and it is listed as a known issue:

Known Issues List 2019 - Updated Dec 12th

September 12th, 2019 Dalaran Heist: Starting a new run will choose the same Hero from your previous run. Note: Ending your current run may allow you to choose a new hero. Titanic Lackey contains a graphical issue. Frostmourne (ICC_314t1) and Soulreaper’s Scythe (DALA_719) deathrattle are not spawning minions. Portable forge does not discover a weapon.