Error (11238): The following 1 fractional PLL locations are already occupied, and the Fitter cannot merge the previously placed nodes with these instances. The nodes may have incompatible inputs or parameters.

Have you tried this solution to a similar issue with Fractional PLLs ?

https://www.intel.com/content/www/us/en/programmable/support/support-resources/knowledge-base/solutions/rd03302012_430.html

To work around the issue, either move the PLL to a different location where there are sufficient GCLK or RCLK resources or change your PLL compensation mode to Direct compensation mode.