do the old "flush the fuel tank" trick!

The clue for me is that after you changed the fuel filters, things were OK, but only for a short while... and now the gremlin is back. Check that pre-filter again and if it is visibly clogged again so soon, then it's flush time... and while you are down there opening that big hole in your tank, you will have ample opportunity to check your screen for it comes out the bottom where you will flush... maybe it's deteriorated and all the "slduge" is carrying forward unimpeded forcing the pre-filter to work overtime.

IF you do end up flushing things, be sure to also blow air or even better force a good strong flow of "fuel" back through the line(s) from the engine compartment towards the tank! Yes, I do mean through both the supply and return fuel lines... pushing the "guck" there back where you can flush it out along with the other "sludge that normally settles in the bottom of the tank.
And for good measure later when you have the tank opened up, give these engine-to-tank line one more blast to clear out anything that worked it's way down from the tank while you were opening her up to flush.

I like to force fuel back through for a liquid is more forceful and thus thorough in cleaning these lines. Then you can use ~3 to 5 gallons of fuel [skimming clean fuel off the top of your bulk container]... use this to flush back into your fill pipe into and through the tank so it will carry more of the sludge out the bottom.
Obviously you do this until and for some time after you see clean fuel spilling out. Flushing can be messy unless you have a cheap pump to use and some way to effectively filter the suction side of your submersible diesel pump. A 12-volt "bilge pump" like those used on power boats might work if you can put together a filter setup around the pump.

You can do this safely only because diesel fuel has such a high flash point in comparison to gasoline with which you would be gambling with your life.

Let us know how it goes,
Sam