[Elecraft] KPA500 and/or KAT500 problem?

[Poul Erik Karlshøj (PKA)]

Just had a problem on the KPA+KAT setup while working on 80m last night. It worked without any problems until that moment, so I'm confident something really did change.
I have contacted Elecraft support, but it occurs to me that someone in this forum might have had a similar experience and may know what has gone wrong.

On a D.L. either directly on the KPA or via the KAT I have a high SWR on the K3 (ATU in bypass mode) as soon as the KPA is set OPER.
I need K3 P= 60W to produce 500W into the D.L , but since the K3 SWR is so high I don't know what power is received by the KPA. Before all this I needed 18W to get 500W out on 80m.

With the KPA in STBY the KAT operates normally on both my antennas with K3 at 100W.
While still on the antenna with KAT having the C and L values found above, as soon as I set KPA = OPER - even with K3 power set to 2W -  I see a very high SWR on both KPA and KAT, while the KPA indicates no current or output power.

I am confused, but probably one single fault can explain this.
Anyone here knows?

73 de OZ4UN
Poul-Erik