Arcam Delta 90 speaker protection relay problem

I have recently aquired a lovely old Arcam Delta90. It sounds lovely and I'm very happy with it, but it does have a problem.

When I switch it on the speaker protection relays switch instantly causing a loud and worrying pop. They should wait 5 seconds.

When I switch the amp off there's a 5 second delay before the relays switch when they should be instant.

I have checked all the caps, fuses and diodes within this circuit and all values seem to be good.

Does anyone have any ideas?

Many thanks
 

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