my Yashica mat 124 has become a bit "picky" : it will trigger fine for a series of images, then will refuse any more triggering until I unscrew the rear lens and "tick" the shutter blades...
Should I lubricate it a bit (it's been CLA'd recently, so I'm not sure it's the issue) ?
Sounds like the shutter needs another CLA. Depending on how it was cleaned, there may still be some old gunk in there. Was the CLA done by a pro shop or a DIYer?
Shutter blades SHOULD NOT be lubricated, that's why they stick. They need to be absolutely dry.
This also includes the blade housing. Any old lube left in place when serviced will keep the blades from traveling properly.
I'll contact the tech who did the CLA, but I'd assume that, since it worked OK for 8 months (I did about 15 films in this period, plus many tests without film), it may not be left lubricant.
A quick update on this. I finally decided to bite the bullet and remove the rear lens element (I bought a 124G I plan to CLA so I first had a look at it) and tried to rub the blades with alcohol... And now the shutter works perfectly ! :-D
Different alcohols will have varying amounts of water. Common rubbing alcohol tends to have the most water of all the readily available (non lab grade) types. Perhaps all have more water than lighter fluid - I don't know.