Tonight, we tracked Vega to test (a correction of) the pointing offset of the Drive.
Around 22:30UTC, we tried different Az offsets of the pointing in the Semi-expert GUI, followed by taking an image with the PSF camera to see the effect of the offset choice.
We tried delta_az = 0.3°, 0.1°, 0.26°, 0.6°. Strangely, we saw some unexpected (much too large) shifting of the spot for delta_az = 0.3° and delta_az = 0.6° (but looked reasonable for delta_az = 0.26°), which appeared quite puzzling to us (see specific Camera Elog here).
After having tracked with delta_az = 0.6°, we stopped again, and selected delta_az = 0.4°. We submitted the command ("Start"). Some seconds after submission, we became unsure whether we used the right field in the GUI where we entered the delta_az values. We hit "abort current action" (to check our previous command), when probably the slewing to the new offset position wasn't finished yet (about 5 seconds after the previous "Start" command). Then, the GUI became stuck displaying "abort current action", and not displaying the field to enter new positions/targets. According to the GUI, the telescope had in fact stopped tracking, but without any possibility to receive further commands.
We restarted the GUI, but the state remained the same, and checked the telescope outside. Then we called the experts, who could solve the problems after some non-trivial intervention.