HP-41CV power-on weirdness

[Adam Vaughn]

Hello everyone. I recently picked up a HP 41CV with no included modules at a hamfest:
   
The seller told me that other than a small amount of corrosion in the battery holder, it was working. I cleaned as much of the corrosion off the battery spring as I could, put in four N cells, and tried to power it up.

The first thing I was met with was a continuous tone from the speaker, which stopped after I removed the battery holder. I then did some more cleaning of the spring, made sure I'd inserted the batteries into said holder (I had), and tried again. This time, I got the expected "MEMORY LOST" message (the only time I've seen it) on the display, which went away after I pressed the "ON" button, but I couldn't get the display to come up again after any amount of pressing "ON".

After doing some Googling, I found an archived post from this forum with ideas, which I tried. Nothing worked until I played around with holding down the Backspace key while pressing the ON button several times, which brought up "CLX" on the display, followed by 0.0000, and the calculator seemed to work normally. Pressing the "ON" button again turned it off, but instead of the problem being fixed, I have to press one of the keys on the keypad (except for the yellow SHIFT key, see below) every time I want to turn the calculator on.

In addition, there's some weirdness in conjunction with this already weird power-up sequence. For example, let's say I hold Backspace long enough that the display shows "CLx" then "NULL", release Backspace, then press "ON" to turn it off. If I then press "ON" again without pressing any other buttons, the display shows "NONEXISTENT", which then goes away if I press "ON" again, or Backspace brings it back to 0.0000. This same sort of thing also happens if I press SHIFT+4 for the BEEP function; pressing "ON" to turn the calculator off, then pressing "ON" again sounds the BEEP tones again, but nothing else happens. Speaking of SHIFT, it nor the other buttons under the display next to the "ON" button bring the calculator up when pressed along with "ON".

I'm sure I haven't found all the weird things associated with this calculator's operation as of yet, but figured I'd throw this info out there as a start. Any ideas as to why it might be acting this way? Thanks in advance!
-Adam