There is a problem with VWs Group powertrains. There was /is a number of engine families with serious faults. Just to name few:
2.0 PD 140 hp, cylinder head prone to cracking. Design fault, later changed.
2.0 TGSI oil consumption, even with VW approved oils with shorter than standard OCIs.
2.0 common rail, injectors fault. It would leave you by the end of the road. Apparently, VW only changed one at the time.
1.6 TDI , injectors fault, not as common as 2.0, but not sporadic either.
1.4 turbo/compressor, too many design flaws to mention. Abandoned desige.
1.4 16v atmospheric unit, many went south before reaching 150k.
Than there is BMWs distribution chain problems on 9x series.
PSA 1.6 16v,109 hp HDI turbo /oil feed pipe fault. Redesigned afterwards to 8v unit.
Renault 1.5 DCI(early ones) were terrible.
Ford Puma 2.2 used in PSA group were utter rubbish, burning holes in pistons wasn't uncommon (injector faults).
FIAT Multiair (early ones) were rubbish, lot of failures.
Toyota D4D head gasket. Engines were redesigned afterwards.