head over to http://mlbs.slipcor.net/ and pick up the last or second to last save fixer
Reseting your Character (position) will fix the sliding - you're not technically on the ground level nor standing upright, despite how your vision may appear.
This occurs mostly when entering water (the intended result of water/swimming) and bugs out occasionally when interacting with the cart or anything else really that can disorientate the player rapidly.
Its best to steer clear of riding in the cart - However, a fairly uneventful ride will likely not cause damage
On the other hand - if you hit abunch of unlevel areas (i.e, rocks) and/or the cart goes bonkers - you can be sure the character position will be flubber nucked...
The Character level sheet will likely also be "off" in the event the character is "off" (Orientation or Position)
When you properly use the Save Game fixer - Your character model will be reset to initial starting position and orientation - in the bed room