The "remove" atomic update action on multivalued int fields fails if the document being changed is uncommitted.
At first glance this appears to be a type-related issue. AtomicUpdateDocumentMerger attempts to handle multivalued int fields by processing the List<Integer> type, but in uncommitted docs int fields are still List<String> in the tlog. Conceptually this feels similar to
It's likely this issue also affects other numeric and date fields.
Attached is a simple script to reproduce, meant to be run from the root of a Solr install.