abstraction boxes suddenly require .maxpat suffix (Mac)

nickfells's icon

A strange one, and no doubt something obvious I'm doing (or not), but in instantiating an abstraction (make a box, type in name of abstraction) the abstraction fails to load (and reports 'no such object' in the console). Typing the name of the abstraction including its .maxpat suffix, and the abstraction loads fine. The abstraction file sits in the same folder as the patch being edited. Even more strange - this only happens with some abstraction files, not others (in the same folder). Ventura 13.5.2, Max 8.5.6 (and previous version had same behaviour). Anyone else had this?