Printer Officejet 4630 - Printing quality suddenly not good. Gaps and spaces along sentences.

[OfficejetJ6480]

Hello.  re: Officejet 4630, Win. 7.       (This is about a different printer -- NOT my member name)

This has worked great for years.  Suddenly there are gaps along sentences. Mostly at the top of a document.  Better towards middle and bottom of page.  Some lines towards top of page are missing the bottom half of the letters along the line/sentence.  But then some sentences below or above a bad line can be fine.

- This occurs when doc is placed manually on printer glass bed.  Printing is fine when printing a doc directly from computer file to printer. So this should be a clue.  Is it something about the "scan" process for a doc laying on the glass?

- There is plenty of ink (both black and color cartridges)

- I have made a cleaning of printer heads twice, and deeper cleaning (I forget what that is called). Not much difference when printing afterwards.

- Note: the printer is at my office that has been used hardly during pandemic since I'm working at home. Despite the oppressive heat this summer in Northeast, the office has air conditioning.  But it has worked fine when I have stopped by the office to pick up mail. I have used the printer just occasionally in those visits over the year and a half.

- There are advertising faxes that come in during my absence. Those copies print fine.  (they are over network and not from a doc on the glass.)

I suppose I could try changing the cartridge, but prefer not to lose the ink (50% is left).  And the ink prints fine when doc comes from computer files.

So what does it mean the problem occurs from the glass only? The print is sketchy over the first several lines at top of page (10 - 12 lines)?

Seems so odd suddenly.

Thank you for any advice or thoughts.