Two double-sided sticky tapes malfunctions in one week! These motors are a bit heavy, so they come down with a bang if they fall off, and break their plywood mounts.
I have (one or two) spares, but that’s literally it for a couple of weeks, so please do be careful and use something very adhesive to mount your motor brackets.
I think it’s important to use some adhesive with a bit of “give”, because the bracket face, and usually your surface are not completely flat and it’s subject to a bit of vibration in use.
I usually use this double-sided sticky foam tape which is very tenacious indeed, but I have also used some temporary “no more nails” tape strips with great success.
Just be careful, I have a few spares, but that’s it!
I just want to remind everyone who hasn’t already got past this bit that it’s very important that you fit the tip for the power supply the right way round. It should be centre-positive. Because the motorshield power supply can, if required, supply the power for the arduino too, there isn’t any reverse voltage protection on the power input, so if it goes in the wrong way round, it might damage either the shield, the arduino, or both.