Oooh, finally got it. I had to back up to some very old code on my part. (still docker master version on your part).
I1007 11:09:37.817001 20 log.go:34] [0] [E] LOG Compact 0->4 (12, 9 → 13 tables with 3 splits). [550469 550527 550530 550534 550545 550547 550549 550554 550560 550564 550567 550571 . 550508 550520 550514 550507 550503 550509 550511 550512 550504 .] → [550580 550577 550585 550592 550594 550578 550579 550590 550595 550596 550581 550587 550588 .], took 2.31s
panic: runtime error: makeslice: len out of range
goroutine 18694554 [running]:
github.com/dgraph-io/badger/v3.(*levelsController).fillTables(0xc0001ce1c0, 0xc015aa1780, 0xc000044000)
/go/pkg/mod/github.com/dgraph-io/badger/v3@v3.0.0-20210916095630-2a9a524b649b/levels.go:1387 +0x453
github.com/dgraph-io/badger/v3.(*levelsController).doCompact(0xc0001ce1c0, 0x0, 0x4, 0x4002e9161999999a, 0x3ffe0e3a62014f9c, 0x0, 0x0, 0x0, 0x4, 0xc00a2d6180, …)
/go/pkg/mod/github.com/dgraph-io/badger/v3@v3.0.0-20210916095630-2a9a524b649b/levels.go:1529 +0x91e
github.com/dgraph-io/badger/v3.(*levelsController).runCompactor.func2(0x4, 0x4002e9161999999a, 0x3ffe0e3a62014f9c, 0x0, 0x0, 0x0, 0x4, 0xc00a2d6180, 0x7, 0x7, …)
/go/pkg/mod/github.com/dgraph-io/badger/v3@v3.0.0-20210916095630-2a9a524b649b/levels.go:466 +0x7a
github.com/dgraph-io/badger/v3.(*levelsController).runCompactor.func3(0xc015aa1f30)
/go/pkg/mod/github.com/dgraph-io/badger/v3@v3.0.0-20210916095630-2a9a524b649b/levels.go:489 +0x158
github.com/dgraph-io/badger/v3.(*levelsController).runCompactor(0xc0001ce1c0, 0x0, 0xc066005ce0)
/go/pkg/mod/github.com/dgraph-io/badger/v3@v3.0.0-20210916095630-2a9a524b649b/levels.go:518 +0x362
created by github.com/dgraph-io/badger/v3.(*levelsController).startCompact
/go/pkg/mod/github.com/dgraph-io/badger/v3@v3.0.0-20210916095630-2a9a524b649b/levels.go:355 +0x89
[Sentry] 2021/10/07 11:09:38 Sending fatal event [48f03d04713045c2a14f76585c4306ad] to o318308.ingest.sentry.io project: 5208688
[Sentry] 2021/10/07 11:09:38 Buffer flushed successfully.