I have used samba share for some time on a USB ssd plugged into the x3000. Worked fine up to and including firmware version 4.4.9. updated to 4.4.11 a month ago and after that downloading a file from the samba share to a mobile device, a Chromebook, or a windows machine all had problems. The file will start to download and the transfer speed drops to zero and then the transfer times out. If I keep restarting the download it eventually finishes. File type does not make a difference. I did a factory reset on the x3000 and it made no difference. I recently updated firmware to 4.4.12 and samba still does not work correctly. Something must have changed in the firmware.
What file system do you use?
The SSD is XFAT. Should I reformat to NTFS? Do you think that might be the issue?
I would recommend ext4 (so the standard linux file system) because it is more stable. But then you can not use the HD in Windows anymore.
I do need to be able to use it in a windows machine as last resort just in case. Would fat32 be ok to use and still be compatible with windows and android?
FAT32 is terrible, would not recommend it.
NTFS might work better.
I have a GL-X3000 with a 8TB SSD and a 4TB SSD (along with a powered USB hub); the 8TB drive is formatted as EXT4 and the 4TB as exFAT. I've also got a 128GB microSD card in the TF slot which is formatted as EXT2. All have SMB shares - and I have no issue with transfer speeds or dropouts (although I do wish that GL.iNet would have put a USB3 port in the GL-X3000); I have and Android tablet, an Android phone, and a couple of laptops running Debian Linux.
The only specific setting I've had to make was on the Android devices to force SMB2/3 (i.e. not use SMB1) - I use Solid Explorer on Android - but I've had to do that all along. That said, I do have an old Brother scanner (from 2014) that connects via 2.4MHz WiFi and saves scans to a shared folder on the GL-X3000 using SMB1 and it doesn't have an issue.
I take it that you haven't made any changes to the GL-X3000's SMB config files? Have you tried connecting a USB flash drive to the router and seeing if it works as a SMB share (in order to eliminate the possibility that there's an isssue with your SSD)? The only other potential issue that I can think of is power (the GL-X3000 only has a USB2 port which USB specs say provides max 500mA) - maybe try using a powered USB hub.