Kohler has good support. You can view the diagrams for that unit with the link I am posting. There are no filters listed in the diagram that might need to be cleaned. There is a chance that the unit has developed a clog from hair etc in the pump impellor. The flange may have come loose and is allowing air in the suction side of the pump too. Kohler has online chat and support numbers you can call too. K-1357-RA ' Devonshire 5-Foot Whirlpool with Apron and Right Drain ' KOHLER
We had a problem with phantom flushing. Call Kholer. They will send redesigned battery holder and top of flush unit for free. Seems to have fixed the issue.
The only batteries are in the docking station. If the remote is attached to the docking station, take that off and set it aside. Next, carefully lift the docking station up and out from the mounting bracket. Look at the back of the docking station, push the two tabs outwards (away from each other) simultaneously to open the battery compartment cover. Replace the batteries (4 AAs) in the correct orientation. Reinstall the cover. Then replace the docking station on the mounting bracket and put the remote back on the dock if desired.
These directions are shown in the Homeowner's Guide (without the service parts) available on the product page: https://www.us.kohler.com/us/veil-intelligent-comfort-height-skirted-one-piece-elongated-dual-flush-toilet/productDetail/toilets/1120267.htm . Scroll down to the Installation section to find the link to the document. The current link to this guide is https://www.us.kohler.com/webassets/kpna/catalog/pdf/en/1226974_5.pdf .
I hope this helps.
Cindy Wells
Smart-a$$ answer is to find an old 3 gallon pot in a salvage place. Best answer is to fiddle with the chain that goes from the handle to the flush flapper and see if adjusting its length makes a difference. If it's too short it might result in letting the flapper closing too soon and allowing your deposit to remain.
There's something blocking it sometimes if you turn the water off in your home and turn it back on sometimes calcium from the pipes break loose and cause blockage in new style washerless valve assemblies.