`deriveRPCWithStrategy` fails on `data` with type variables

Description

It looks like, at least in some cases, deriving a customGeneric on a data with a type variable and then trying to derive an AsRPC instance with deriveRPCWithStrategy results in a compilation error.

Steps to reproduce

Ass this test to Test.AsRPC:

----------------------------------------------------------------------------
-- Data type with type variables and custom generic strategy
----------------------------------------------------------------------------

data WithTypeVariablesStrategy a = WithTypeVariablesStrategy
  { _wtvsField1 :: a
  }

deriving anyclass instance IsoValue a => IsoValue (WithTypeVariablesStrategy a)
customGeneric "WithTypeVariablesStrategy" haskellBalanced
deriveRPCWithStrategy "WithTypeVariablesStrategy" haskellBalanced

data ExpectedWithTypeVariablesStrategyRPC = ExpectedWithTypeVariablesStrategyRPC
  { expectedWtvsField1 :: BigMapId Integer MText
  }
  deriving stock Generic
  deriving anyclass IsoValue

_checkWithTypeVariablesStrategy :: ToT (WithTypeVariablesStrategyRPC (BigMap Integer MText)) :~: ToT ExpectedWithTypeVariablesStrategyRPC
_checkWithTypeVariablesStrategy = Refl

_checkWithTypeVariablesStrategyLaws :: ()
_checkWithTypeVariablesStrategyLaws = checkLaws @(WithTypeVariablesStrategy (BigMap Integer MText)) Refl

Note: the problem doesn't seem to be restricted to a specific strategy, any can be replaced above and result in the same problem.

Expected behaviour

The testing snippet above compiles successfully.

Actual behaviour

An error similar to:

The exact Name ‘a_aAZe’ is not in scope
  Probable cause: you used a unique Template Haskell name (NameU), 
  perhaps via newName, but did not bind it
  If that's it, then -ddump-splices might be useful

is raised.