I'm curious to learn more about your Turbo 040. You indicate it is the 33MHz version, but is the to of the card (CPU side) similar to one of my two photos? (My B&W photo shows the Daystar User Manual version of the card, which is older. My photo of the actual 40MHz card in my possession shows the latest hardware.)
Also, do you know what ROM version you have on your Turbo 040? As I mention under my Daystar Turbo 040 photo, I have the latest 4.11 version ROM. The card actually came with an older ROM, but the seller (Manabu Sakai of ARTMIX, maker of the TS Adapter) upgraded the ROM for me, for a $59 fee (allowing me to keep the old ROM chip). But even with the newest version ROM, I still found that I could not READ/WRITE 1.4MB floppy disks when I had a non-stock SE/30 ROM in the machine. But when I put in an SE/30 ROM, the floppy drive worked just fine. Currently, I have a 50MHz DiiMO in my SE/30, which is slower than the 40MHz 040, but it's more compatible and I have no problems at all with READING/WRITING to 1.4MB floppies with any ROM, be that the stock ROM, IIfx ROM or IIsi ROM. So there appears to be an incompatibility with the Daystar Turbo 040 and IIfx/IIsi ROMs -- a problem that doesn't afflict the DiiMO accelerator. I confirmed this problem on an older 25MHz Turbo 040 too -- hardware that matches what you see in my B&W User Manual photo (and lacks the 128kb cache card).
But if some of you run the same tests as I and find no problem, then perhaps I could say it is the TS Adapter. Because again, I am not using a Daystar Adapter in conjunction with my Turbo 040 -- I use the TS Adapter. Manabu Sakai contends it is not a problem with his TS Adapter because he claims his adapter is 100% the same as the Daystar version, with the exception that the TS Adapter allows you to insert more than one PDS card in the SE/30 at the same time.
So I guess my question is, Equill, do you have a IIfx or IIsi ROM? If so, I would love to hear your test results in combination with 1.4MB floppy disks. Ditto for anyone else reading this post who has a similar setup.