I've noticed a bug that popped up recently with the steel bladder perk changes in the Awesome mod, I only noticed it after installing Pets a while ago.

Sims with a steel bladder only partially fulfill their bladder need when you tell them to go. It'll fill the bar up around 1/4 of the way, then they'll stop. You have to tell a Sim with a steel bladder to use the toilet 3 or 4 times for them to max out the bladder need. Sims without a steel bladder however always max out their bladder motive the first time they use a toilet.

Also this is probably related, but I noticed a sim without a steel bladder fills their bladder need 2300+ an hour when using the toilet (according to the numbers you see when hovering over the motive bar), but a sim with a Steel Bladder only fills their bladder need 560+ a hour. Perhaps this is part of the problem, if a sim only uses the toilet long enough to fulfill the bladder need for a sim without a steel bladder, even though sims with steel bladders take longer to fill their bladder motive bar.