I don't think it's good practice keep the RV in "Store" mode when plugged into shore power. I inadvertently did that on an RV and noticed the 12 volt lights flickering when the water pump turned on. I suspect that the converter is working extra hard to maintain enough current and voltage for the lights, water pump, and other 12 volt requirements.
During long-term storage I do not connect the RV to shore power. I know it's convenient, but some converters are not sophisticated enough and will over charge the batteries. When storing I put the RV in "storage" and I have a disconnect on the coach batteries. I use two battery maintainers to keep the batteries in good condition.
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