Hi, Ignord!
I use RG58U on the dual Plasma I's on my Lancair. Some of the RG58,
under heat with a short radius bend, had the center conductor
occasionally shorting to the braid. This was more of a problem with
foam dielectric rather than polyethelene. The RG400 has a much higher
temperature range. If you have the foam dielectric cable and have some
tight bends you might consider either straightening out the cable more
or, if that's not possible, replacing with the RG400. Of course, your
problem may have another source, so you might want to do a little
substitution/swapping trouble-shooting . Paul