Wrong count on items in collection

Overview shows 126 items, but only 125 are listed.

https://musicbrainz.org/user/ernstlx/collections

https://musicbrainz.org/collection/9a531957-1cad-46e4-844b-7b195de65c89

Not important, but might point to a bigger problem.

(I will extend this collection, so the numbers might change)

 

EDIT: Idea for a possible cause: 2 releases were merged, both might have been part of this collection at this moment.