The arcing is definitely concerning. Do you have another amp to verify that problem so you can say it is the amp or the tube? Regardless, I would contact Dennis Had (or however you purchased) for advice. Assuming it has a soft start feature, the current behaviour seems contrary to intended design. I hope you can get this resolved easilly!
Thank you for your impressions on the two suppliers. With a complete lack of stated selection parameters it is difficult to decide what/if there are differences. Even if there are differences, we have no credible research data that those differences correlate to sound quality, reliability, length of time in which sound quality is comparable to the 100 hr mark, and so on. Tubes are gonna fail when they want to, NOS included. I had 1 fail at @150 hours, Viva Tubes had a matched replacement at my door in 4 days, cross country. Dealing with out of country can be more complicated and expensive. I don't think there is anything wrong with deciding what kind of buying experience we want to have. Recently I bought a oem replacement light for my car from Latvia as those things are tough. Tubes are fragile, for me Im fine paying for Stateside screening and rapid replacement. YMMV!
I have a full set of 6 Linlai HiFi black plates on my Cary SLP-05. Enjoying them a lot, but will do impressions and comparison later when I buy a full 6 of the E-6SN7s.