I have had several occurrences in the past few months where I make a backup, download the .zip file, and verify that I can open the .zip file without any issues (since if a .zip file is extremely corrupted, it won't even open), and restore it. The restore goes through correctly but when I start using the restored 3CX I am unable to register any new extensions (I can add new extensions but the phones themselves will not register), BLFs do not function reliably, and calls do not transfer reliably. This does not happen every time but it does happen occasionally. Even though I am making the backup, downloading the .zip file, and uploading it on different machines on different networks, the same issue has a chance of occurring, and has occurred in the past. This means it is not an issue with the specific machine or network I am uploading or downloading the backup from. To resolve this issue, all that 3CX needs to do is integrate some sort of MD5 verification (checksum) on the backup .zip file. This way, I will know 100% that the backup file does not contain any corrupted files (as even if the .zip file can be opened and browsed, there is a chance that one or two files did not backup properly inside of it). I realize that this would incur a high CPU usage, especially for large backups, but if verifying backups via hash/checksum was optional via check box, users with lower-power 3CX servers could leave it disabled.