MC Version: 1.12
Forestry Version: 1.12.2-5.8.2.422 (Enigmatica 2: Expert)

Unlike the regular Peat Farm, the multi-farm does not return the dirt left over once peat is produced, making it difficult to automate bog earth production.

I'm also having this same issue, which has appeared since January.

Facing the same issue. Likely related: tree farm also does not return sand after replacing degraded humus. Thanks a lot for workaround with single-block peat farm, it works perfectly!