So here’s my setup:
and here’s one of my shots:
It seems this issue is pretty common with the EFH but I’m also wondering could it be the 40mm? I’ve learned that’s pretty short for a macro lens for a set up like this. Any help would be greatly appreciated!
Come on, you know pretty well it’s EFH . You just don’t want to accept that you need spent money on another film holder. 
Firstly please can you confirm that this is from a colour negative that has been ‘processed’ and whether it is from 35mm or 120 (6x9), maybe you could even upload a photo of your setup with the Raleno panel.
I don’t have an EFH but I’ve seen plenty of comments about it on here and other places, and you will have done also. Clearly if he’s sold 40,000 of them then not everyone gets these problems so I think that I’d agree that having a shorter focal length lens doesn’t help. With your example it’s quite strange that the left edge in your image above is affected much more than the other, I don’t understand that, normally in other posts it has been both long edges.
Personally with any setup like this, not just the EFH, I would want to make sure that my light panel is masked down to an aperture that is only slightly larger than is necessary for that film format, and I’ve also seen others find that removing the bottom diffuser layer has eliminated the problem. If you do this then you need to be sure that you are far enough from your panel to get even illumination and no artefacts from the individual LEDs.
@kgigler , do you scan your negatives in a dark room? Does the gradient change when you reposition the EFH over the backlight? Or rotate the backlight, will the gradient follow that move?
Any chance of light reflecting back onto the negative, like from a white t-shirt, wall etc., other stray light e.g. from a computer screen?
Anyways, first test without negative and see if you still get the gradient.
Yeah I’ve heard this is a pretty common issue, any viable alternatives?
The first thing that stands out is that the light leak is only on the left-hand side. If the problem was on both sides, then I’d say it’s most likely the film holder. I also had this exact issue with stray light happening only on one side. I’ve tried different setups and learned it really does matter where your setup is in a room. For example, are there any windows nearby? What time of day do you scan? At night or with sunlight outside? Is your setup right next to a wall? It even matters what color your wall is. Is it white (highly reflective) or a darker color? Are there any metalic/shiny objects near your setup? Such as the shiny legs of a tripod or copy stand? Things that we don’t notice, the camera notices. Really look around your room and observe the light and reflections.
The light leak is on the “flag-side”, so check which direction this side of the film was facing when it was in your film holder exacting as it was when scanned.
Good luck!
