Mac SMB inaccurate available space

Here's my setup:

2016 macbook pro with touchbar (High Sierra)

Linksys EA7500 router - per their specs, the hard drive is approved for sharing, and the routers supports NTFS, FAT, HFS+.

WD passport 2TB hard drive, and a sandisk 4GB usb drive attached to USB 3.0 ports on the router.

The hard drive and usb drives have been formatted to Mac OS Extended (Journaled), Mac OS Extended (non-journaled), or FAT32 during my various attempts to access them.

When I access the hard drives through smb://192.168.1.1 (as the router states), I'm able to see the drives and mount them. I can copy small files to them. However, both drives only show a 40mb available space. Intermittently they will switch to their respective sizes (2TB and 4GB), but then later switch back as per Finder. This means that I can't effectively copy or move files over 40mb since it doesn't see more available space. This 40mb space decreases as I add small files to it.

I have tried this with a friend's windows computer and it's not an issue. Therefore I believe it's the way the mac handles SMB (I seem to have read similar issues in the past on forums). Is there any way to address this? Any workaround?