Map Boss not accompanied by a synthesis boss

Running a zana-influenced thread map (Mausoleum), I rolled the 'Map Boss is accompanied by a Synthesis Boss' modifier, but no synthesis boss ever spawned when killing Tolman. Bug report reference number 1,455,392,963

Just had the same thing happen to me in a memory thread map (Temple, in my case). No synthesis boss in sight, bummer. Bug reference 1,027,097,884

Same. T16 Vault. Rolled Magic, other mod was "Area has patches of Awakeners' Desolation"

Second quest memory thread-line spawn (have killed the first of 3 quest bosses). Have 2 voidstones, so the map is normally T15/shows as T15 on the atlas, but was T16 as offered by Eagon.

T16 Chambers of Impurity - same thing, no Synthesis Boss spawned. Bumping.