Hi Patrickr +
how often does the fault "won't end after ball five" happen ? once in ten games ?

See the JPG - encircled "rosa / pink" are switches (I believe) currieddog is mentioning in his post-38. When the Q-Game-Over-Relay does pull-in for a moment - but then quit pulling: These encircled switches and/or theirs wiring can be the cause of the problem (not seeing Game-Over in the Backglass).
Play many ONE-Player-Games --- when the fault happens: Look at the lights on the players score-drums - see the bottom of the JPG: The drums on Player-1 probably are lighted by "switch P1F on the Player-Unit" --- how about the other drums ? The drums on player-2 and -3 are lighted when the BX-Relay has actuated - on player-4 when the Q-Relay is pulling --- what is lighted in Your pin when the fault is happening ?

Target Alpha is a very late - very modern EM Pin --- the Coin-Unit is made to reset to its "sub-player-1-resetted-position" - I show in the JPG what happens in a ONE-Player-Game when the player looses the fifth ball. Early in play the DX-First-Ball-Relay was made to actuate - "encircled green switch DX" is closed --- now it is the last ball in a ONE-Player-Game - all the time playing the last ball the Player-Unit is in position-16 (my green curved line) - the ball is then lost, bonus is counted / given - the O-Ball-Return-Relay pulls-in, stays pulling (, makes the motor to run). Through "encircled green switch "O", closed as O-Relay now pulls: The BX-Relay is made to actuate. Now comes "my blue stuff" - the motor turning closes its encircled-blue switch and BX-Relay and O-Relay are pulling - the switches are closed: The Coin-Unit is made to reset (!). Now comes "my red stuff" - Through the resetted Coin-Unit the Q-Game-Over-Relay is made to pull-in.

See the fault "my brown stuff" - when the BX-Relay is faulty not made to actuate --- its switch is closed --- the pulling O-Relay (switch closed) --- the Ball-Return-Kicker (Outhole-Kicker) fires and the ball comes out into the shooter alley ...

Patrickr - what do You see on the Score-Drums lights when the fault is happening ? Do You have some ( SteveFury 's ) 24Volt-Test-Lights - (each) Test-Light has two cheap 12Volt car light-bulbs one mounted behind the other. Greetings Rolf

0Target-Alpha-Work-37 (resized).jpg

Hi Patrickr
great - You work again on the Target Alpha. http://www.pinrepair.com/em/index.htm is a great site - lots of good information --- here http://www.pinrepair.com/em/index3.htm#axrelayvideo is an video about adjusting these AX / AXR, BX /BXR etc. relays. Later in the video Clay shows in detail the adjusting - but the beginning of the video is also interesting. Clay talks about the transition from (example Far Out) huge Control-Bank to the later Gottlieb pins not having a Control-Bank - having these AX etc. relays. Look from the start of the video - then at 1:35 to 1:46 see the AX-Relay actuate - shortly after the AXR actuates. I guess in post-48 "I can push it in with my hand and play a game" means: At the end of the start-up You manually actuate the AXR.
You then write about "not ending a game properly". Of the same type as AX / AXR You have in Your pin the BX / BXR Interlock-Relay. The BX / BXR relay usually is mounted near the AX / AXR relay --- play some balls - before playing the last ball: Take the ball out, lift the playfield and secure it --- manually make a couple of points - then park Your finger in the Outhole (You simulate "Last ball drains, enters the Outhole) - AND watch the BX / BXR relay - does it actuate - it should actuate after bonus-points have been given, O-Ball-Return-Relay pulls-in.
See the JPG in post-39, on the left, rather down - encircled green the coil on BX-Relay - then to the right in the JPG the wire-of-color-OR-BLK to "Switch on O-Ball-Return-Relay" - then wire-of-color-OR-WH to the Player--Unit. Look on the O-Relay in Your pin for this switch - wires soldered-on ? switch properly gapped ? contact-points clean ? (((Of course wire can be broken-off at Coil on BX-Relay, wire can be broken-off at Player-Unit, Jones-Plug in the connection may be faulty (((BX-Relay (and O-Ball-Return-Relay ?) is/are down in the Cabinet, Player-Unit is up in the Backbox - there is an Jones-Plug))) ))). Greetings Rolf

Hi Patrickr
see here https://pinside.com/pinball/forum/topic/player-unit-gottlieb-4-player-game-royal-flush#post-4842927 in the lower right corner of the JPG: The switchstack on the (black) fifth cam on the Player-Unit --- the switches that have to do with "the pin has done the start-up / reset - ready for Player-1 will soon launch and then play Ball-1". Greetings Rolf