Hello,
I believe that this issue had been discussed here before, but I recently observed a non-reproducible issue with my LX which had been professionally serviced by Advance Camera. Very occasionally, my LX would be stuck with mirror locked up after completing an exposure in AUTO mode. From the rolls that were developed during the past, it seems that the exposure was made successfully, but the mirror won't return unless I turn the shutter dial from AUTO to 2000.
However, it happened once every few shots yesterday, and I had suspected that my battery was dying, so I replaced it with a fresh pair of LR44 batteries (I have been unable to get SR44s here in China, just LR44s). But this issue continued to persist for three or four times before it completely disappeared. I suspected that my LOMO Volna 50 1.8 could be the blame (since my copy had a plastic aperture guard too long that actually blocked the movement of the mirror, and had to be ground down) so I switched to my FA43, and the issue almost immediately disappeared, and I have not been able to reproduce it since then, even with my LOMO lens.
Digging the forum, I found
Pentax LX mirror stuck up in AUTO only - PentaxForums.com but it seems to be a persistent electronic issue that completely disables AUTO, which is very different from mine. However a follow up mentioned that LX can be a bit picky about batteries. I would like to hear some suggestions on this issue.
Sincerely