Another one damaged by folk who can't tighten a bolt! Tbf many garages don't even have 3/4" socketry, so just tighten it as best they can and send them out. Sooner or later they come loose.
Does sound like a bent valve as won't let you get it on time, but will turn over if out sightly out of time? If you do get it timed up, worth doing a compression test to see what you have. Think 24 bar is at the low end, these will mage 30 bar per cylinder if in top shape.
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