How to clean prolog ?

[Hemery-M]

Okay, the title may not be exactly the problem but I have a strange bugs that appear when I try to solve multiple queries (more that 1000 but less than 300.000). At a point, Python just crashed and print

[FATAL ERROR: at Tue Dec 14
	Too many stacked strings]
Abandon (core dumped)

Each of the query is really fast but it seems that stacking them without properly clean the prolog part leads to this failure !