Firefox won't allow uploads above 2MB

[jshster]

Anyone had issues with Firefox only not allowing uploads beyond 2MB? Same site on Chrome and Edge works perfectly for files up to 12MB (won't go beyond that due to memory issues). On Firefox it will let you select the file but as soon as you click Start Upload it fails with an "Unknown Error". Nothing in the Javascript console. Nothing in the PHP error log.

I have opened Firefox in Safe mode - problem still exists
I have refreshed/reset Firefox - problem still exists

I actually don't think this is a ResponsiveFileManager issue but just wanted to find out if anyone else had experienced this problem and if they had a solution?