The only problems off hand that I know of are:
The G21 and G20 (and IIRC, the G29 and G30), at one time had problems with light strikes on hard primers. This was caused by the cruciform on the rear of the trigger bar not being high enough and letting the firing pin go a tad early. GLOCK remedied this. Old trigger bars are marked 4256 and new ones are marked 4256-1.
The G36 had mixed issues when new. Alot of people were just having a tough time gripping it right, and alot of them were just jam-o-matics. GLOCK tweaked them a good bit, and new ones are good to go.
The new G21SF has had hit and miss problems with out of spec trigger bars that produce a very heavy and gritty trigger pull. I have not heard of a specific serial number range they are falling under, and as far as I can tell, they are just replacing them on a pistol by pistol basis.
Nothing terrible out there, new models have problems, and get fixed.
Those are of course the .45ACP pistols.
GLOCK also has a line of .45GAP pistols. The G37, G38 and G39. None have had any real issues that I am aware of.