Hafler Amp puzzle

I have a Hafler SE-120 amplifier and one side of the amp gets hot even when at Idle. I suspected that the bias needed adjusting. The manual states that the bias should be set at 100ma so I measured the settings according to the service manual and the left channel was spot on at 100ma but the right channel creeps up from 50ma to over 250ma then just peggs the ammeter. It does this regardless of my trying to adjust the bias pot. I have de-oxed the pot to little effect. 
FYI the amp sounds fine. 

Also, it looks like at some point someone replaced the output mosfets on the side that's getting hot. 

Any ideas will help.
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