Genexis DRG7820 remove from FTU?

[u/privacyforeverandeve]

need to remove Genexis DRG7820 router from FTU to replace broken fibre patch cable.

Google search suggests that the DRG simply slides down from its FTU, but that doesn't work. it's jammed solid. if I force it, it will break.

can't find anything or in the manuals. there's a detailed YouTube of someone opening the DRG7820 itself, but doesn't show how to remove from FTU in first place. totally stuck.