Randomly wrong phpBB web root path calculation on our IIS server

What version of phpBB are you using? phpBB 3.3.0 What is your board's URL? https://dynoinsight.com/phpBB3/ Who do you host your board with? HostDime How did you install your board? I used the download package from phpBB.com What is the most recent action performed on your board? Update from a previous version of phpBB3 Is registration required to reproduce this issue? No Do you have any MODs installed? No Do you have any extensions installed? No What version of phpBB3 did you update from? phpBB 3.0-B1 What styles do you currently have installed? prosilver only What language(s) is your board currently using? English British Which database type/version are you using? MS SQL Server What is your level of experience? New to PHP and phpBB What actions did you take (updating your board; installing a MOD, style or extension; etc.) prior to this problem becoming noticeable? This was noticeable in v3.0 also. Not it became worse, possibly because of increased traffic. Please describe your problem. I often get a plain text view of the whole board. A white background with bullets. Mostly after I login or log out. It is random. Sometimes it works fine for hours. Sometimes I can not use it at all