Changing the seed for the student is certainly a good fix. It won't change the problem for the student since it is a static problem. It doesn't have a single random parameter.
So that problem does not work very well. I see warnings already when the problem loads with that seed. Then when I enter the correct answer I get the "Can't generate enough valid points for comparison" warning. The problem is caused by a poor choice of function for r(x). The function is sin(x/e)^pi - cos^2(pi * x). What happens is that sin(x/e) can be negative, and then that is raised to the power of pi. Negative numbers can't be raised to non-integer powers. It is a bit odd that this doesn't happen more frequently for this problem. I guess the odds of sin(x/e) being negative are not that high?
I any case, I don't get the error that you get. Just the warnings. Admittedly, warnings that prevent the problem from functioning as intended, but not fatal errors.
Looking at the Encode/Alias.pm module installed on my system (the default package for Ubuntu 22.04), I don't see anything on line 22 that would cause the error message that you are getting either. However there is a "require" statement on line 104. I am guessing that you have an older version of that module that has something similar in it. Since this is in WWSafe "require" calls are trapped and you get that error. In any case, this may be an issue with the version of that module that you have installed. One thing that is odd is that for the file on my system, that "require" statement will only occur when the PERL_ENCODE_DEBUG environment variable is set. It is also a little odd that the Encode::Alias module is called at all here. That module is not shared with the safe zone, so that alone should cause a problem. It seems that the warnings in that problem are triggering this for your server setup for some reason. I wonder if warnings of any kind from PG trigger this same error for you?
So that problem does not work very well. I see warnings already when the problem loads with that seed. Then when I enter the correct answer I get the "Can't generate enough valid points for comparison" warning. The problem is caused by a poor choice of function for r(x). The function is sin(x/e)^pi - cos^2(pi * x). What happens is that sin(x/e) can be negative, and then that is raised to the power of pi. Negative numbers can't be raised to non-integer powers. It is a bit odd that this doesn't happen more frequently for this problem. I guess the odds of sin(x/e) being negative are not that high?
I any case, I don't get the error that you get. Just the warnings. Admittedly, warnings that prevent the problem from functioning as intended, but not fatal errors.
Looking at the Encode/Alias.pm module installed on my system (the default package for Ubuntu 22.04), I don't see anything on line 22 that would cause the error message that you are getting either. However there is a "require" statement on line 104. I am guessing that you have an older version of that module that has something similar in it. Since this is in WWSafe "require" calls are trapped and you get that error. In any case, this may be an issue with the version of that module that you have installed. One thing that is odd is that for the file on my system, that "require" statement will only occur when the PERL_ENCODE_DEBUG environment variable is set. It is also a little odd that the Encode::Alias module is called at all here. That module is not shared with the safe zone, so that alone should cause a problem. It seems that the warnings in that problem are triggering this for your server setup for some reason. I wonder if warnings of any kind from PG trigger this same error for you?