Oil cooler down after timing chain snapped repair

Had my timing chain snapped (bmw 520d 2010) and it has
been fixed for £4400!!! but...couple days later oil cooler
went down (oil leak underneath and when opened the oil
cooler it was full of high pressured engine oil) The garage
said it's definitely not related to the recent repair - I
disagreed as was driving the car for over 2 years with no
issues whatsoever and in my opinion it had to be realated
to the original repair if happend just couple days after I
have picked the car ...
What do you think?
I think the engine oil pressure  was too high for sone reason
after the repair and cause the oil cooler damage...