If possible, I would suggest that you upgrade to the latest release: 184.108.40.206.0. It has many bugfixes and enhancements.
There is no limit on the number of optionals per query. I suspect that the use of the same new variables (?avgrec and ?maxrec) in the parallel optional clauses is the reason you are seeing the error in this particular case. If you use different variable names does the error go away? If needed, you can use a coalesce in the outer SQL SELECT to get the same behavior as before (e.g. COALESCE(avgrec1, avgrec2) as avgrec).