some of the CdS meters had filters to colour balance in tungsten cause without they are red and near red oversensitive. In tungsten they will overreact if they did not have a filter

some CdS cells have lost some low light sensitivity

the Mercury oxide batteries are no longer available you need a Wein style cell or a silver cell with Shockety diode most repair people would use a label after fitting a diode. Using an alkaline won't be reliable.

David has not mentioned the state of either cameras repair or indicated what the user manuals say

David could review the manuals, inspect the battery, and try again?