I see several threads in the forums on this issue now. But yes. We were bit this past weekend and unfortunately coincided with an internet service upgrade, and CPE swap, which after banging our heads collectively on our desks turned out to be red herrings.
We are on MX250's and were at 16.16, which updated to the 17.10. last Sunday evening.
We were seeing pages not loading and "err_timeout" messages, but then hitting reload would work. Also, pages or sites used widely in the company worked fine. Like, Office 365 pages would load. But a site that had not been previously visited would then not load or it would timeout. But then if you reloaded, or revisited the site, it would work for a time.
We stayed late last night with SD-WAN provider engineer, as we thought it may be related, and were unable to reproduce the error at all over a 90 minute period. The difference is that it was after hours, and there was hardly any traffic on the internet connection. The next morning as people returned to the office, the problem returned. We rolled back the firmware at that time and service was restored.
My gut says this appears to be some sort of inspection or cache component failure.