hi looks like you have isolated the problem to the pump
you have a few options from here depending on your skill level with using tools
1/you can call in help to remove and repair pump
2/ you can isolate the problem further.
if you go with option 2, this is what I would do
remove the four cap screws from the solenoid groups from both pumps and swap them.
you have to be careful as there are small o rings and a feed back lever to engage
if the problem moves with the swap that is the problem
if the problem stays where it is it is a mechanical issue internal to the pump
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