Not quite sure this will help, but did you try to right click on the second motion and select "Align" right or left foot?

I'm having the same problem. Depending on the situation the sliding can be out of control. Hoping someone has some suggestions.

I'm running into a LOT of trouble in regards to transformation keyframes on my character. I have several imotion files I purchased from truebones, and one for example is a simple walking motion, which works fine on its own. The problem comes into play when its combined with a different clip, because the character transform travels a distance on the grid, and then the first clip, after having walked a distance, warps to whatever position the second motion clip starts at. 

I've tried several things including going to animation>motion setting options and I tried every combination available. The only noticeable difference I noticed was that if I check "Allign actor motion" then the root stays with the character, and if "Reset motion root" is checked, then the root stays at the center, but the character walks off without it. 

I've tried making lots of transform keyframes hoping that I can eventually allign it up properly, but all I get is crazy sliding all over the place.

I've tried sampling the motion clip, but transform data isn't available for sampling.

I've tried watching several basic animation tutorials to see if they conquer this or a similar problem, and I've yet to find an example.

I'm super appreciative to anybody that can help me solve this problem!