Googling around this type of thing can be caused by if eg: Windows suspects files have a virus, so you start to d/l them and its then “intercepted” by your Antivirus Program or Windows Defender and removes / quarantines it so you carn’t save it anymore as its gone.
So If you have any optional Antivirus / Security program installed, try disabling that temporaily to see if that makes any differance when saving. Failing that, try disabling temporarily Windows Defender.
If it then works by disabling Windows Defender, either you have a problem with a recent eg: Windows update and “you may need to roll back and do the update again” or the files you are saving may actually have some form of Virus or Malware / Spyware in them.
Some users also reported “to fix this issue”, they disabled the “Controlled Folder Access” in Windows Defender Win 10 which may have been caused by a recent Windows update that set it to “On”. Mine is turned off on both my pc’s by default so check that option to see if it makes any difference.