Extend Home - Occasional Conversation dropped during call

Have a Moto e6 used ONLY with extend home service. Numerous occasions when talking, the other party can no long hear our end. It cuts out while we still can hear them. When recalling by the other party, same thing happens. Calling with our other non-RW cell phone service (Pixel 4XL) (not connected to extend home service) call works fine. Initially thought it was our 4 year old Panasonic KX-TGF375 home phones. Now we don’t know. Did the usual resetting of modems and Grand Stream Extend adaptor - issue still reoccurs from time to time. Annoying but would like to know cause and fixes if possible.
jimk

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