Modpack version
1.80

Issue
Item Placeholder in Epic tier reward,
exchangers:resonant_exchanger/0

looks like the resonant exchange is still in the rewards table despite the mod having been removed in favour of the building gadget.

Relevant change log.
1.80
Using Forge-1.12.2-14.23.5.2847
Exchangers Outclassed by Building Gadgets, sorry :(

Logs
N/A

Thanks for the report :D