Rear Shifting Problems

[Ajax Bay]

I never thought of adjusting the limit screws

I'd just gently point out that 5 minutes after the OP posted his issue, @Globalti had provided the solution which would have taken a minute to execute.
https://www.parktool.com/blog/repair-help/rear-derailleur-adjustment

 

[Ajax Bay]

derailleur . . . . lower jockey wheel had collapsed.

Do share an image of the failed pulley wheel.

 

[nmfeb70]

I'd just gently point out that 5 minutes after the OP posted his issue, @Globalti had provided the solution which would have taken a minute to execute.
https://www.parktool.com/blog/repair-help/rear-derailleur-adjustment

As did @C R. As I said in my post at 18.31 on Friday, I couldn't understand how adjusting the limit screw would make a difference because the shifting was precise on the smaller front chainring. Thanks anyway.

 

[MrGrumpy]

Do share an image of the failed pulley wheel.

Might be hard to see but lower pulley waggles quite a bit. Teeth are not too bad but small bearing has collapsed. To be fair this derailleur was bought 2nd last year and has never been right ! New R7000 fitted and it ( touches wood) worked great on a test ride .