stack overrun expression error

Running the calculations inside a single expression where you can control the processing order should avoid these problems. Otherwise you're facing long hours debugging this by turning off individual expressions, changing your slider values and then repeating this forever until you find the culprit. In my hayday I used to create dedicated "Control" layers for this that held a ton of point controls and sliders just to calculate those values. Not only does it avoid evaluation issues, but is also much easier to re-use and streamline than drilling inside specific expressions on tons of individual layers.

Mylenium

You are likely creating an internal race condition. None of your expressions actually check whether the other has worked its magic, in particular the various sourceRectAtTime() uses. It would be smart to pack such stuff inside a single expression on a dummy control, then only read out the values the control produces via simple pickwhip expressions. Point in case: All your expressions work on their own, but you may run into scenarios where they produce implausible values and cannot determine which parts evaluate after one another.

Mylenium

Without any info about your project, where the expression is applied and what the code actually is nobody can tell you much. Simply sounds like you created a "greedy" expression with bad code and/ or applied it to a property that does not handle the values the expression generates correctly. Relying on AE's safety mechanisms to save your bacon sounds like a bad approach to handling this...

Mylenium