Thank you Gentlemen, turning off the sound notification does indeed solve the problem! Sorry for not thinking about this.
Just in passing, here is another non-critical issue which happens frequently with high acquisition rates. As you can see below the image file numbering scheme is quite erratic at times:

-rw-rw-r-- 1 bertin bertin 4248000 Feb 21 23:49 NGC2683_Light_0.500_secs_2018-02-21T23-49-11_1938.fits
-rw-rw-r-- 1 bertin bertin 4248000 Feb 21 23:49 NGC2683_Light_0.500_secs_2018-02-21T23-49-12_1939.fits
-rw-rw-r-- 1 bertin bertin 4248000 Feb 21 23:49 NGC2683_Light_0.500_secs_2018-02-21T23-49-13_1939.fits
-rw-rw-r-- 1 bertin bertin 4248000 Feb 21 23:49 NGC2683_Light_0.500_secs_2018-02-21T23-49-14_1940.fits
-rw-rw-r-- 1 bertin bertin 4248000 Feb 21 23:49 NGC2683_Light_0.500_secs_2018-02-21T23-49-15_1940.fits
-rw-rw-r-- 1 bertin bertin 4248000 Feb 21 23:49 NGC2683_Light_0.500_secs_2018-02-21T23-49-16_1941.fits
-rw-rw-r-- 1 bertin bertin 4248000 Feb 21 23:49 NGC2683_Light_0.500_secs_2018-02-21T23-49-17_1941.fits
-rw-rw-r-- 1 bertin bertin 4248000 Feb 21 23:49 NGC2683_Light_0.500_secs_2018-02-21T23-49-18_1942.fits
-rw-rw-r-- 1 bertin bertin 4248000 Feb 21 23:49 NGC2683_Light_0.500_secs_2018-02-21T23-49-19_1943.fits
-rw-rw-r-- 1 bertin bertin 4248000 Feb 21 23:49 NGC2683_Light_0.500_secs_2018-02-21T23-49-20_1944.fits
-rw-rw-r-- 1 bertin bertin 4248000 Feb 21 23:49 NGC2683_Light_0.500_secs_2018-02-21T23-49-21_1945.fits
-rw-rw-r-- 1 bertin bertin 4248000 Feb 21 23:49 NGC2683_Light_0.500_secs_2018-02-21T23-49-22_1945.fits
-rw-rw-r-- 1 bertin bertin 4248000 Feb 21 23:49 NGC2683_Light_0.500_secs_2018-02-21T23-49-23_1945.fits
-rw-rw-r-- 1 bertin bertin 4248000 Feb 21 23:49 NGC2683_Light_0.500_secs_2018-02-21T23-49-24_1945.fits
-rw-rw-r-- 1 bertin bertin 4248000 Feb 21 23:49 NGC2683_Light_0.500_secs_2018-02-21T23-49-25_1945.fits
-rw-rw-r-- 1 bertin bertin 4248000 Feb 21 23:49 NGC2683_Light_0.500_secs_2018-02-21T23-49-26_1945.fits
-rw-rw-r-- 1 bertin bertin 4248000 Feb 21 23:49 NGC2683_Light_0.500_secs_2018-02-21T23-49-27_1945.fits
Nothing serious but worth mentioning.
btw, is this forum the best place where to report and file specific bugs? I have started to dig into the code, I will try my best to help.
Thanks!

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