As a person who has taken a good look at the EF service manual, and have disassembled my EF, what happens is the following: For some usages the camera require 1.35V, for others, 2.70V. Thus, depending on the selection of the flash modfe switch (CAT vs NORMAL), the connection of the batteries will change between series vs using only one battery.
BTW it will work indistinctly with 1.35V or 1.5V cells because the silicon photo diode is amplified using an operational amplifier. Thus, gain of the amplifier will not depend on power supply voltage! Well done Canon!
This Operational amplifier IC is very static sensitive, so it shouldn't be touched!
This is an easy fix.
See above explanation.
The battery holder has the inner positive and negative contacts beneath very close, separated by a very thin film. Humidity and corrosion will make havoc. Of course this is a very easy thing to fix. Many "electronic failures" on electronic cameras are just... the camera getting no power from the battery compartment!!
My EF had such a problem, but in this case the camera did work, however the batteries drained quickly. Cleaning the wiring and contacts beneath the battery holder and introducing electrical tape as additional insulation cured the problem.
... because the long speeds depend on the two batteries connected in series. Solve the battery compartment problem and the long shutter speeds should work.
This explains why you are leaving Canon! (emphasis)
If you like the EF, you might LOVE the F-1, particularly the New F-1.
I sold my EF, i didn't like it as much as my F-1 cameras. I even liked the A-1 more. There are people who say "the EF is the electronic version of the original F-1". This is bulls$%$$, internally they are completely different and the build quality of the F-1 is even higher. High, to an standard hitherto unseen on japanese cameras, making potential users lust passionately and making users salivate with delight upon touch. Better fit and finish than the Nikon F, F2 and the F3 (all of them wonderful cameras of course). I have owned all these cameras, so speak from direct experience.
However, the EF was priced at close the price of the F-1. This might explain why they were not a best-seller...