Coset table calculation failed -- trying with bigger table limit

Question

I tried with the following code snippet in GAP:

f:=FreeGroup("P","Q");
g:=f/ParseRelators(f, "P^2 = Q^3=1");
Size(g);

But it gets stuck in the following step:

gap> Size(g);
#I  Coset table calculation failed -- trying with bigger table limit
#I  Coset table calculation failed -- trying with bigger table limit
#I  Coset table calculation failed -- trying with bigger table limit
#I  Coset table calculation failed -- trying with bigger table limit

When I terminate the command by Ctrl-C, and then run the last command, the following result is returned:

brk> Size(g);
16384000

Such a simple relationship leads to such a complex group, which makes me a little confused.

Regards, HZ