Typewriter randomly returns to left and finishes typing what was in the memory. Sometimes it returns to the left and shuts off.

make sure the right hand platen knob is tight hold the platen and turn the knob top toward the back of the typewriter until it is tight

It's either in the carriage lock position, just check if it's locked in place.
The other reason may be that the return spring has broken. Easy to replace & is repairable sometimes.

The Selectric typewriter has several "interlocks" that can cause the keyboard to be locked. When you turn the machine off there is a mechanism that locks the keyboard. When you turn it on the part should move and unlock the keyboard. Sometimes this part sticks and the keyboard will remain locked. When you type any character the keyboard is locked to prevent two keys trying to type at the same time. The machine locks and unlocks very fast. One keys is locked in and prevents others from working. try turning on the machine and hitting every key just a little bit harder and see if it then types. When you shift, as the ball is turning the keyboard is locked temporarily so it won't attempt to type as the ball is turning as that would damage the machine. Sometimes the shift mechanism can cause the keyboard to remain licked as the shift may not have finished it's complete cycle. Also, the return mechanism locks the keyboard temporarily when the carrier is returning to prevent you from typing when the carrier is moving backwards. Only a qualified technician can resolve those issues.

There is no keystroke pattern to reset the EM series typewriter. There are two methods to reset this typewriter.
1.You can reset the daisywheel and remain on the same line of type, simply lift the top cover and then close it back down. The carrier will move to the left, reset the daisywheel and return to the last space typed.
NOTE: This will not affect the format settings (bold, underline, etc)
2.If you want to abandon the current typing position; turn off the typewriter, wait 10 seconds for the power supply to reset and then turn the typewriter back on. The typewriter will reset and the carrier will return to the beginning of the current line.
NOTE: Turning off the power will restore the format settings to standard default settings (bold, underline, etc).

Try this Spray a little WD40 on the silver shaft that the carrier slides on. If that dosen't work you must lube the carrier motor bearings, to do this you can access the front one from inside the machine the rear one depending on the age you can slip the straw thru the case or on the newer ones you must remove the case.

DickyO

Try a little WD40 on the silver shaft that the carrier slides on.

DickyO

I have worked on typewriters fo 20+ years.
The only typ's I know of that had the return on the right hand side are all the manual typ's

1press and hold the code key and type the # 1 thru 99 wher you want to store the job(chose any one number)
2 the store light should blink
3 the ARtn light comes on
4 the carrier returnes to the left margin
4 the printwheel spins
5you may begin typing when the store light is on solid
6 let the carrier return automatically at the end of each line of type

7close the store when finished by pressing and releasing the store key

You must have damaged the Daisy Wheel when you were fitting c'tape..Fit another wheel..