hmm, works for me in Ventura 13.6.9: dbl-click to open a movie > File > Export > Export Frame to Pictures -- exports the desired frame to ~/Pictures as .tiff.
Does it work for a plain vanilla new .mov from iOS/iPadOS? Does a detour to safe-boot fix it? Is the Photos library on a APFS or MacOS Extended (GUID) volume?
Remove all 3rd party virus apps (Avast, AVG, Bitdefender, Intego, MacAfee, Norton, ESET NOD32, Trusteer etc) and 3rd party "cleaning", "optimizing", "speed-up" apps (CleanMyMac, MacKeeper etc). They produce only obscure errors.
An EtreCheck report would eliminate much guesswork:
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