Especially for Tough Resin, it’s important that you use relatively clean IPA. This is much of the reason we recommend soaking in one container for a few minutes and then finishing the part in another. You might try soaking in the first container of IPA for 10 minutes or so, then remove the part in soak in the second for another 10 minutes. Make sure that the second bucket is relatively clean as this is important for removing all of the excess resin from the part.