This is a 3-part counterpoint I am working on. It is not a strict counterpoint exercise but I want to try keep within the guidelines as much as possible. In m. 19 the middle voice (in red) stops leaving the outer 2 voices forming 5ths on beat 4 of m. 19. Then in m. 20 I have an 85 chord with the middle voice forming parallel 5ths with the bass. Is this a case of parallel 5ths?
I would argue that this is fine. There are plenty of instances in "classical voice leading" where something like this happens, and although it may sounds like parallel fifths to some degree, the realities of the voice leading prove that they aren't.
It may be worth considering including a rest for that middle voice on beat 4 to clearly show that the voice momentarily drops out, but that's really only for academic purposes (i.e., if you're submitting this score for an application). Otherwise, I think you're free to leave this like it is.