My solution to a slight noise problem was to use a small toroid and wrap the 4 nextion leads through it.

I run a nextion 3.5 on my ubitx without additional regulator. Added in a heat sink to the existing 7805. Have not had a problem in the 2 years that it has been that way. 

Is your radio in a metal case?

Perhaps a high pass filter may be needed for BCB interference. 
--
73
Dave
ADOB
Raduino bracket and Ham_Made_Keys