For my Taz5 printer support had me put 4 Taz6 wiper pads under the heater to support it as a temporary fix.
I am attaching the picture below on how the pads were arranged. The pads actually do support the head bed up against the glass and has uniform heating across the glass bed.
If your printer is a Taz5 I would mention this to support as my heated bed went back and forth 3 times before they came up with the temporary fix. You might ask about a permanent fix too.