My Elna 8600 won't quit stitching when I lift my foot off the foot pedal.

Something must have come undone mechanically. You will need service unless you want to try and strip the machine to look for it.

you have a fault no one else has

https://www.google.com/search?q=Elna+Contessa+320+presser+foot+won%27t+lower+far+enough+to+reach+material

..

Most likely it is a foot control problem--probably something you cannot see.

When you unstuck the pedal, did you also go inside to unstick the contacts (switch). This happens sometimes for lack of use. You may need to replace the contact, but you will see when you get in there. GOOD LUCK FRIEND.

It is likely that your elna graph gear is broken.
remove thread from machine and open door to where you put cams in. Step on pedal and run at full speed. It the mechanism where the cams go spinning? If not the gear is broken.

The Elnita is the entry level model in the Air Electronic compact series, there is no reverse lever or button. Instead, you stop stitching, turn the stitch length dial back to zero, then keep turning into "negative" area, it should look like this "-- --- ---- -----" on the dial. Turn it back about half way into the negative area and you will get a reverse stitch of about 2.5 or so. Do your reversing stitches, then stop and turn the dial back to original forwards stitch location, and continue sewing.

sounds like there is a short in the wiring and the machine need
to be checked

only having the machine check at a sewing machine repair shop can say for sure

It sounds like the food pedal is sticking. I have had this happen only to find that the pedal had drifted under my mobile thread drawer and was unable to lift up when I took my foot off it - yikes - looked like a ghost was operating my machine! However, it you are sure the foot pedal is not stuck under a piece of furniture, perhaps the spring inside is not decompressing completely. It needs to be checked. I am not that familiar with the Emerlad models - do they have a Stop/Start button on the machine itself? If yes, perhaps this button is stuck in a little? Check that also.

Is this the duplex model with the base that fits into a sewing cabinet?

My Elna booklet lists a SP "air electronic" duplex (CL.39), if so, then it would be same stitches as the 38, yellow front panel, 7 built in stitches and automatic knob with blue markings for buttonholing.

Here is the SU manual images for buttonholing, should be exactly the same for the SP.

Instructions are:
use buttonhole foot. turn the 3 dials to buttonhole marked in blue (stitch selection, width and length).
Mark length of buttonhol on the material. Place work under foot with the mark in the middile fo the foot, the start being directly below the needle. sew the first side, raise the needle. Turn stitch width dial to 2, blue. Sew a few stitches for bartack. Raise the needle.
Turn stitch width dial to 3 blue. sew the second side. stop just short of the first side. Raise the needle.
turn the stitch width dial to 4 blue. sew a few stitches for bartack. Raise the needle.
Turn stitch width dial to "fastening off stitch" blue dot. Sew a few stitches, holding back the material by hand. Raise needle, lift pressure foot and remove work, triming off threads.
Open the buttonhole with your seam ripper (put a pin across the end to avoid any nasties).

It sounds like the timing may have to be reset or adjusted - it happens, so do not be alarmed.

Open the needle plate, remove the bobbin and bobbin case and clean away any lint or thread snips that may be there.

Re-thread the machine with the presser foot up - always.

If there is still a problem find a dealer who will service the machine for you.

The Elna site should have dealer locations.