While you wait for your damping there are a couple of things you may want to check to make sure you don't have a cabinet leak or standing wave issues inside the cabinet:
1) Did you add a gasket to the tweeter? My tweeter was supplied without a gasket so I had to buy some speaker gasket tape for the tweeter, making sure that it also covered the side holes I had to make for the tweeter terminals to fit through the baffle
2) Although plastic would not be my first choice of material for crossover boards (I used 6mm mdf), you may want to consider rubber grommets rather than foam to isolate them (stronger and more robust). Rubber grommets screwed down into the base at each corner should help mitigate any board vibrations
3) I have mentioned in a previous post the lack of current research regarding speaker damping materials, but what seems to be generally accepted is that natural materials with complex fiber structures (natural wool, denim, felt etc.) are better than artificial fibers (polyester, foam, rubber) at absorbing standing waves inside speakers. You may want to experiment with this.
4) Damping should be placed on all internal walls except the baffle and the floor (if the crossover is placed there). it's particularly important that the rear wall is fully covered (with cutouts for the port and speaker terminals).
Further details in the assembly instructions at the bottom of this page:
https://nbaudio.com.au/blogs/projects/customer-project-mechano-23