[Elecraft] KX1 tuner bypass question

[NZ8J]

When I bypass the internal tuner and feed my external autotuner (on any of
the 3 bands), the external tuner will match my Zepp very well with less than
a 1.3 : 1 swr. The KX1 shows about 4 watts out using an external supply,
however when the swr indication comes up on the KX1 display it shows a very
high SWR, sometimes as much as 9.9:1.  I don't think that is a correct
reading, but wonder if anyone else has experienced this. The internal tuner
works fine and the swr shows a correct reading when using the internal
tuner. Putting a MFJ 259B on the coax that was connected to the KX1 shows
the same SWR  readings as the external tuner, so I suspect it is something
with the internal swr indicator. any ideas??
thanks
Tim
Nz8J