Maybe unrelated but as you are on Windows and using a 64bit perl (assuming this from the path name) you might be interested in Win32::SerialPort finally fixed for 64 bit Perl leading to this fix.

I can confirm that I can reproduce the bug using the OP's code with the $PortObj->read(1) method on a 64-bit Strawberry Perl, but the same code does not produce the error on a 32-bit version.