Tommm glad to note that you found the direction to solve the problem.
I had some time this morning to further look into the differences between LR and PS.
With same image in LR and PS both in softproof mode, measuring RGB values at same spot gives these results:
Spot 1:
App R G B
LR: 197 192 186
PS: 178 179 173
Spot 2:
App R G B
LR: 23 8 18
PS: 11 7 0
If not in softproof (LR in develop, PS in normal view):
Spot 1:
App R G B
LR: 192 193 187 (75.4%, 75.6%, 73.4%)
PS: 179 179 173
So to summarise: some difference - although curious enough - but not the issues you experienced and found the cause for luckily.