Bruno and Marc,
Thanks for the interest. My source for this little puzzle is Louis Leconte's 1937 study Le Regiment Royal Liegeois au service du roi de France 1787-1792. Its dated but M. Leconte did yoeman work in the Archives de Guerre and his footnotes are treasures. Yes the regiment did experience a riot at Avesnes in early March 1790. Susane stated that 600 fled to Mons. Leconte mentions 400 but even that figure is suspect.Following such events it was standard practice to move the regiments and the Royal Liegeois was sent to Sarrelouis. At about the same time Bouille sent the regiment Picardy there also. After being forced to witness another incident involving Picardy the Royal Liegeois were sent to Wic. This was related in Comte H. de Liedekerke-Beaufort's memoire, Soirees de Noisy. From Wic??? the first battalion was then sent to Nancy as part of Bouille's force. It was only after the affaire de Nancy that the Royal Liegeois was sent to Belfort. The Mulhouse area seems a bit far for the regiment to travel and then be used at Nancy... But.... its a puzzle.