Until others with firefox 64 test the links for download we'll know if it is really a firefox issue or not.

Clicking on the start link gets this:

404. That’s an error.

The requested URL / was not found on this server. That’s all we know.

First Link I get this:

Google Drive can't scan this file for viruses.

[Drivenime] Or-Mongtar!! BD 480p.rar (1.3G) is too large for Google to scan for viruses. Would you still like to download this file?

Second link:

Whoopes! There is a problem with the preview "retrying"

Then option: "download"

So at this point my trying on firefox 64 doesn't support what your saying that it's a firefox issue.

If you use extensions ("3-bar" menu button or Tools -> Add-ons -> Extensions) that can block (wanted) content (Adblock Plus, NoScript, Disconnect, Ghostery, Privacy Badger, uBlock Origin) always make sure such extensions do not block (wanted) content.

• make sure your extensions and filters are updated to the latest version
• https://support.mozilla.org/en-US/kb/troubleshoot-extensions-themes-to-fix-problems

Firefox shows the shield icon at the left end of the location/address bar in case Content Blocking is blocking content.

• click the shield icon for more detail and possibly disable the protection

You can check the Web Console about what content is blocked

• "3-bar" menu button or Tools -> Web Developer
• https://support.mozilla.org/en-US/kb/tracking-protection
• https://support.mozilla.org/en-US/kb/content-blocking