I had the same problem.
Wpengine.. networksite all under CloudFlare.
I've also reset the Db cleaning old data but the problem remain.
502.. it's seems the plugin need to much time to update DB and we have 502 from the server.
I was investigating with some collegue this morning when i discoverd that after reset the stream db a few tables are still large: ex: gryt3mt_stram has 43,075 records.
Now i'm using 1.4.4. The updating process of db dosn't work since the last update.
now i saw that there's a new version.. but i think i need to solve this problem with db before.
tnx in advance for your support