Mercurial: Uncommitted local changes are detected while there are none

Question

Hi to all mercurial pros,

I'm facing a very strange issue with Mercurial. There's a repo with 2 heads. If I clone it, update to one of the heads and try to merge the other, it refuses because of uncommitted local changes. How can that be with a freshly cloned repo? Hg status does not show anything, hg commit says there are no changes. Furthermore, if I force the merge and try to commit afterwards, it tells me that it cannot because of missing files. Hg status still shows nothing, hg commit says there are 21 missing files, but does not list them. I'm absolutely out of ideas, would be happy to hear any.

Mercurial version: 6.6.3 (TortoiseHg), no extensions active except standard OS: Win10 and 11

C:\Users\ar\judo> hg clone -U docs docsclone

C:\Users\ar\judo> cd docsclone

C:\Users\ar\judo\docsclone>hg log -G

o  changeset:   13:00e42bc1d80c
|  tag:         tip
|  parent:      11:2636897b57e0
|  user:        alre
|  date:        Sat Mar 16 23:40:29 2024 +0100
|  summary:     fixed DT handling in results export script
|
| o  changeset:   12:258250141287
|/   user:        indo
|    date:        Sat Mar 16 23:36:59 2024 +0100
|    summary:     JMP 2024 done + results exported
|
o  changeset:   11:2636897b57e0
|  user:        alre
|  date:        Fri Mar 15 23:03:43 2024 +0100
|  summary:     prepared tournament files JMP 2024 
|

... (clipped)

C:\Users\ar\judo\docsclone>hg update 13
4404 files updated, 0 files merged, 0 files removed, 0 files unresolved

C:\Users\ar\judo\docsclone>hg merge 12
abort: uncommitted changes
(use 'hg status' to list changes)

C:\Users\ar\judo\docsclone>hg status

C:\Users\ar\judo\docsclone>hg status --all
C .hgignore
... (clipped; shows all Clean)

C:\Users\ar\judo\docsclone>hg commit
nothing changed (21 missing files, see 'hg status')

C:\Users\ar\judo\docsclone>hg purge --all

c:\Users\ar\judo\docsclone>hg update null
0 files updated, 0 files merged, 4383 files removed, 0 files unresolved

c:\Users\ar\judo\docsclone>hg update 13
4404 files updated, 0 files merged, 0 files removed, 0 files unresolved