Hi TomBeals,
When you describe the printer as 'sometimes' refusing to print full pages, would you say that there is any consistency based on the program you are printing from? it is possible the issue is stemming from a particular program like Adobe or Microsoft.
Please check for Windows Updates if you have not done so already. If the issue is intermittent and occurring randomly from multiple programs it could be the driver. If you feel the issue is the driver, or related to the computer some how and not a specific program, or the printer hardware itself, I suggest using the HP Print and Scan Doctor. The Hp Print and Scan Doctor can quickly resolve many printing and scanning errors, network connection problems, and driver issues. Click here to download the utility.
Hope this helps.