I have installed 5.4 several days a go on a x86 that has about 900 PPPOE clients. It crashed after a day and I had to downgrade to 4.17 again. I had the same problem with 5.2 and I'm hardly waiting to see it solved and install 5.x version. Arash Did you sent autosupout.rif to support@mikrotik.com ....