Just been getting this LUA error recently when trying to sync DKP (merge only, full-broadcast works fine). Have tried reinstalling the addon, deleting the saved variables, disabling all addons except Monolith, still no luck. Here's the LUA error:

Message: Interface\AddOns\MonolithDKP\Modules\Sync.lua:470: attempt to index field '?' (a number value)
Time: Thu Sep 3 00:04:46 2020
Count: 1
Stack: Interface\AddOns\MonolithDKP\Modules\Sync.lua:470: attempt to index field '?' (a number value)
Interface\AddOns\MonolithDKP\Modules\Sync.lua:470: in function `MonDKP_SyncDeleted'
Interface\AddOns\MonolithDKP\Modules\Sync.lua:231: in function <Interface\AddOns\MonolithDKP\Modules\Sync.lua:209>

Duplicate of #375