Problems with Shimano Steps E6100 electricassist.

This is actually my husband's problem with his bike, but I thought one of you might be able to help. Here's what he says: "I have an ICE trike with a Rohloff hub and Shimano Steps E6100 electric assist. I really like riding it but I am having persistent ongoing problems with the motor. When climbing hills the motor assist occasionally decreases as if I had switched from ’High’ or ‘Normal” to ‘ECO’ or off, but the displayed boost level doesn’t change. I can see the ‘effort’ or current bar decreases and becomes noisy (Shimano doesn’t seem to explain what is being displayed). The problem seems to occur when the current bar is above half. Changing the boost level doesn’t seem to have any effect. Sometimes shifting gears restores the assist. Today just hesitating pedaling briefly restored the assist. Once, last fall the motor entirely shut down with an error message (I don’t remember what one, but it wasn’t helpful) and the motor was dead for 30 minutes. I talked to the dealer who I think talked to ICE and they recommended I coat the battery terminals with NOALOX, an aluminum wiring cleaner. I did and and didn’t have any problems until warm weather this year. And the shutting down entirely hasn’t reoccurred. Except for that one time there have been no error messages. I have two batteries (for longer rides) and the assist fade problem occurs on steeper hills with both.
Does anyone have any idea what is happening?"