DIAGNOSIS The robot's internal backup battery that saves the map when it's powered off is failing, or a software glitch is corrupting the saved map data.
FIX First, try a full reset of the robot's software. In the Ecovacs app, find the robot settings and perform a 'Restore' (not just a reboot). This will erase the current map and all settings. Then, create a brand new map by sending it on a full cleaning run. Do not move the dock or major furniture after this.
IF THAT DIDN'T WORK The problem is likely that weak backup battery. When the dock's main power is interrupted (even briefly), it loses the map. Ensure the dock is plugged directly into a wall outlet, not a power strip that gets switched off. If it is direct and still happens, it's a hardware fault.
HEADS UP If you manually pick up and move the robot to start a cleaning in a different room, it can get confused and decide the old map is invalid. Always start cleaning from the dock.