Upgraded a Manticore Intimidator shotgun and a Manticore Executioner sniper rifle to G5. Applied four mods to each including scope. All mods appear to work except the scope mod. Also acquired a G3 TK Aphelion rifle with Scope mod included from Pioneer Supplies but it only had the default mini-scope, not the upgraded one. Wrote to Frontier Support and was told "We are aware some players are having issues with some upgrades, such as the scope. This is currently under investigation, and is a known issue... We do not have a way of fixing this on our end, but as mentioned, we passed your details on so we can help resolve this in any way we can."
Since they could not fix at their end I assumed that meant I should try something at my end. So purchased and upgraded a new Intimidator shotgun to G5 and applied the scope mod as the first mod. Of course that did not work either.
So no scopes for me until this is fixed. But at least the engineering materials are much easier to come by since the T8 update and on-foot missions and combat are a lot of fun, even without the scopes.
I left my vote and reproduction details on the
Issue Tracker. Please add a vote if you can.