Fermenter bubbling again after 3 weeks lagering

[seanjwalker1]

Hello all. I'm sure this question has been answered but I'm really tired of searching years old threads. In a nutshell..fermented 5 gallons wee heavy at 64° for 3 weeks in a Cool brewing bag. Airlock bubbled away for first 5 days then by day 7 stopped. I completed the 3 week Lager at 64° then let the fermenter warm up gradually to room temp, about 70°. Well on day 2 of warming up, my airlock started bubbling at a pretty good rate again! I wanted to transfer to a secondary after 72 hours diacityl rest..but it's still bubbling! What gives? I used S-04 yeast 1.5 packages. I've lagered a few times and this has never happened. Should I wait for the bubbling to slow down again before I take a gravity reading? Thanks