Warning re JJ KT77s

I've recently had a terrible reliability experience with these tubes. I needed four for a Jadis Orchestra Reference - I purchased a second set as back up, that is eight KT77s in total. Within two months two of the JJs had burned out, drawing massive current, lighting up like fireworks, and in the second instance blowing the fuses in the amp. During this time three others had developed annoying hums or crackles.

For two years previously the amp had run without bother with a set JJ KT88s. And prior to that for a year with EHKT90s. So I don't think the amp is the culprit. At every change of tubes the amp was professionally biased by the local Jadis technician.

Some threads here, and at other sites, speak highly of the KT77's sound - I thought they were fine, but preferred the KT88s overall. What's more threads, and some dealers, warn of the JJ KT77s awful reliability - here I can only agree!