[Elecraft] KPA1500 gain jumping on 160

[Steve Masticola]

Has anyone else seen the kind of gain jumping on 160 shown here?
https://www.youtube.com/watch?v=LjfksHwLz9w
The exciter is a K3, and I generated the drive signal by putting it into TUNE mode. The KPA1500 is feeding directly into a dummy load, so the antenna, etc. is not the cause.
I believe I heard about a "160 gain reduction mod" to correct this problem, but I can't recall where I saw it.
73, -Steve WX2S