Updated to latest MCMT 0.22.87 for 1.16.5 and it fully starts up to completion, then just explodes...
This is being used with MAGMA 1.16.5

[05:28:06] [MCMT-Pool-Thread-0/INFO] [or.jm.mc.mo.FastUtilTransformerService/JMTSUPERTRANS]: sync_fu it/unimi/dsi/fastutil/longs/Long2ObjectOpenHashMap$FastEntryIterator Transformer Called
[05:28:06] [MCMT-Pool-Thread-0/INFO] [or.jm.mc.mo.FastUtilTransformerService/JMTSUPERTRANS]: sync_fu inner class of Lit/unimi/dsi/fastutil/longs/Long2ObjectOpenHashMap;
[05:28:06] [MCMT-Pool-Thread-0/INFO] [or.jm.mc.mo.FastUtilTransformerService/JMTSUPERTRANS]: sync_fu it/unimi/dsi/fastutil/longs/Long2ObjectOpenHashMap$FastEntryIterator InnerClass Transformer Complete
[05:28:06] [MCMT-Pool-Thread-0/FATAL] [ne.mi.co.ForgeMod/]: Preparing crash report with UUID c1903978-5b19-4837-b963-29ed0c56cf2d
[05:28:06] [MCMT-Pool-Thread-0/FATAL] [ne.mi.co.ForgeMod/]: Preparing crash report with UUID be808173-ee77-403f-9e69-f2a397f01f54
[05:28:06] [MCMT-Pool-Thread-0/FATAL] [ne.mi.co.ForgeMod/]: Preparing crash report with UUID f3b39ebe-c7e5-4bd0-b526-e2723b5ad2f7
[05:28:06] [MCMT-Pool-Thread-0/FATAL] [ne.mi.co.ForgeMod/]: Preparing crash report with UUID 33d74bd4-4d02-4562-9997-0e324aadd54c

It will spam this infinitely until the server process is killed.

Log:
latest.log