I've been struggling to decipher the undocumented errors that the ODE Solver VI has been giving me the past two days, and I wanted to report my findings here to aid anybody else that may be fighting with the same issues. Also if you run into different issues and find the solution then post your findings here for posterity. Note that I was using the "formula string" instance because it seemed much more intuitive when sharing my code with non-LV'ers, so some of these errors will probably only show up when using that instance.
Error code, problem and solution
-23087, the input arrays (the formula strings 'F(X,t), variable names 'X', and initial values 'x0') are not all the same length. Remember that each differential equation is with respect to one variable, and each variable can only have one initial value, so all those array lengths need to match.
-23088, your formulas include a variable with an illegal name. Remember that variable names are VERY limited, as documented on the page https://zone.ni.com/reference/en-XX/help/371361R-01/gmath/variables/, i.e. a single lower-case letter (not including 'e'), or a single lower-case letter (again excluding 'e') with a single digit.
Enjoy!
