Please use "Reply all" :-). That's strange, the following code, with both reinstating a \set Staff.timeSignatureFraction or \unsetting it works for me:
\version "2.20.0"
\relative c' {
\set Staff.timeSignatureFraction = 4/4
\time 8/4
c4 d e f g a b c
\set Staff.timeSignatureFraction = 3/2
\time 3/2
b a g f e d
e f g a g f
\set Staff.timeSignatureFraction = 4/4
\time 8/4
c4 d e f g a b c
\unset Staff.timeSignatureFraction
\time 3/2
b a g f e d
e f g a g f
}
Perhaps a Minimal Working Example from yours or alternatively the file you're working on could help us guide you better.