I got an answer from the french support, stating that my product was defective They invited me to contact my reseller to return the router. I contacted Amazon that will refund me. The interesting...

I have been experiencing similar freezes on my R480T+ v6 (5.2.2 Build 20140422 Rel.59193s) too. The up time ranges from 24h to a week or so. I also had no-ip ddns activated and have just switched it...