I am not sure about the source for base you affirmations, but as far as I know this behaviour is standard.
Any incoming jobs should be kept on the HDD and released when the machine has required resources available.
A diferent behaviour could be cause by a firmware bug on which I would try a NVM Reset, (make sure to print a config report before you apply any of these settings in case you loose you configuration), if this will not solve a firmware upgrade.
Eventualy you can also look at Image Overwrite on the machine, this could cause the HDD to wipe your data in case of memory need for basic features or even based on time-stamp.
If non of this works you might want to have an engineer to have a look at it.
Hope this helps,
Just found out that this ADVANCED machine does not have capability to hold the faxes in case it can not print!!! We just had an issue with one of the color inks being low so machine stopped printing. So we are going to loose all the incoming faxes as they were not printed and now gone.
Checking up with support - understand that this advanced machine lacks the basic fascility of storing the incoming faxes eventhough it has lot of memory and hard drive!!! This sounds ridiculous as even a cheap machine these days would have that feature available as a standard and makes logical sense.
What were the product designers thinking while building this machine or is it a deliberate omiission?? And you assume that such features which are now industry standards would be included but not at XEROX!!! And ofcourse they do not tell you upfront either.
Is there any other work around then keeping another fax machine handy, in case of problems with the machine?