This looks like an internal error.
> (cd rust && cargo test -- repro)
thread 'repro' (1345333) panicked at /home/dan/.cargo/git/checkouts/egglog-7c9491f597880af0/53b9721/core-relations/src/offsets/mod.rs:136:9:
slice is not sorted: [RowId(13), RowId(1), RowId(2), RowId(3), RowId(4), RowId(5), RowId(11), RowId(12), RowId(13), RowId(14), RowId(15), RowId(16), RowId(17), RowId(18), RowId(19), RowId(20), RowId(21)]
This looks like an internal error.
Reproduction (far from minimal): code
UPD: I do know about #911 and #914, but this is on the latest commit (53b9721 in panic message)