[Elecraft] [K1] Unusual ATU Problem

[Elecraft Reflector]

Hi Guys! I wonder if you can help with a bewildering problem please?

I have a K1 with a 4 band board (40, 30, 20, 15m) and the internal ATU. All function perfectly and match to an inverted Vee cut for 30m. On 30m my analyser shows a Vswr of around 1.1-1.3.

I have recently added a 2 band board for 80/30m with the same Elecraft ATU. The ATU matches 80m to the same antenna with no problems. However when I activate tune or key up with the 30m part of the board, strange things happen. The screen goes clear,  the following lights show in sequence: Attn light fashes - green RIT - red RIT - some relay chatter - Attn light - Display resumes. 

If a power meter is installed in line with the antenna feed, the same sequence occurs and no power registers.  It gets stranger...!

If I connect the K1 directly to a dummy load the ATU tunes up as normal. No problem.

If I put a 1:1 or 2:1 balun in series with the antenna the problem occurs but if I put a 4:1 balun in series it works just fine.

I have remelted every solder joint on the board and checked no components on the board are touching above or below. 

Without the ATU the board provides 5W to the antenna on 30m easily.

If I pop back the 4-band board and ATU combination, 30m works via the tuner with no problems at all.

I am bewildered and perplexed. Any ideas would be much appreciated. Thanks Guys

Steve - M0ECS