I run this transmitter also and my range testing showed 150m+ to be fine in open areas. However I had a drop out during a weekend bash session at about 80m. The area was humped so I could only just see the car from eye-level. I re-ran the area at a slow pace and I had no issues.

Reading your post and having experienced the issue in the weekend I did a little testing, positioning the transmitter at my usual hand held "angle" with the aerial in it's default upright position. I put in in one side of the house and tested the the receiver lock by taking the car through several rooms out into the garden and down some steps etc (about 50m total). I then adjusted the transmitter aerial to a more upright position using the adjustments it has and redid the test.

The results of my test was that having the aerial in an upright position made a big difference to performance in challenging conditions (drop out count 1 vs 7).

In this testing the receiver seemed to re-gain it's lock quickly but I did have some different issues with another car I run. In this circumstance the receiver would sometimes power reset on full throttle taking 3 or 4 seconds to re-lock. I tracked it down to the combo of a poor ESC bec circuit and a low capacity battery. A cap plugged into the receiver overcame this issue. I don't need the cap on my main car which has a better ESC.

Hope this helps.