Are we talking about Lotus Elise and the use of the K series engine again?
K series wasn't too bad for reliability in the mgf and Elise.
With the eventual upgrade to steel dowels and polymer coated head gasket the reliability woes were halted.
When tuning them as long as the bottom end is well balanced then they aren't really an issue.
Jags 3.0v6 was an upgrade from the 2.7 engine essentially the same as nford and PSA designed it but with larger capacity. Unfortunately although they knew the issues with the 2.7 they elected not to rectify them, this was down to cost, as essentially they would have to redesign the block and crank, cylinder spacing, ancillary components etc etc,
The issue with these engines is the main bearings are to narrow.
I believe they thought the number of failures compared to the actual cost of development wasn't financially worth while. Unfortunately they did not take into account the damage to the brand.
The ingenium engines would be reliable if it wasn't for the dpf system, when performing regens it needs excess fuel to do it, unfortunately in some models it doesn't get hot enough and others gets too hot, and basically fills the cylinder block with fuel most people don't realise and engine failure ensues, I don't think jlr are any worse in this regard than most manufacturers it just gets shouted about more/picked up by the press.
BMW had major issues with timing chain failures, VW has damper pulleys falling off on engines, ford previous gen and current gen transit and ranger engines randomly snap any rotating equipment, very costly failures with emission systems and fuel injection bla bla bla.