I would like to add that the SS4709 reel chip can be used for three other games as well as "Double Black Jack".
They are: "Double Black Tie"
"Double Red, White & Blue"
and "Hot Peppers" - the strips and glass kit that is installed on this particular machine.
I installed two vastly different SP GAME chips to see if there was any difference in the Credit lamp behavior when credits were accumulated.
The 1st SP GAME chip I installed was the SP731.
It is one of the oldest SP chips I had on hand and I didn't see any unusual Credit lamp behavior.
The only that is "supposed" to happen is that the Credit lamp remains lit steady when there ARE credits accumulated.
I then installed a vastly different SP GAME chip into my S+ test machine which was also a TYPE 0 SP chip.
I wanted to try something different...
The GAME chip I installed 1st was the much older SP574.
Then I installed a later SP1271 chip.
Again, no usual Credit lamp behaviors and no "flashing" of that switch's lamp after installing all three different TYPE 0 SP GAME chips on my test machine.
In summary, I could not introduce the "flashing" deck button behavior into my test machine.
Can you verify for me the colors of the 4 individual wiring pin locations on that Credit button?
I want to know what wiring colors are connected to the two switch pins and the two lamp pins.
I am suspecting a possible incorrect connections on that button or something wrong with the door wiring harness.
There no events programmed into any S+ SP chip that can cause a deck button to "flash" intermittently as far as I can recall.
However, there ARE programming for the candle lamp to flash on top of the machine and another one.
I fear somehow that the flashing signals are coming through the door harness wiring and crossed somewhere with the display panel flashing signals for when the door has been opened without playing one complete game or the alike data signals that are intended for the candle for that event.
The two lamps that light up on an S+ display panel are the "Coins Inserted" & the "Coins Played" lamps.
Just for kicks, with the power off, disconnect the 3 door wiring harness connectors from the top of your MPU tray panel and reconnect.
Do the same for the left-most Molex connector that runs to the candle.
Then lift up/remove your MPU board and re-install.
None of these actions will hurt your machine as long as the power is "OFF".
After reconnecting various Molex connections, power up your S+ and let us know if the flashing condition has went away.
Sometimes a data signal gets entered & stuck into the system and repeats itself over and over.
The only way to remove a "stuck" signal is to break circuitry or reset the machine back to original factory settings
and configurations via a Clear chip.
We've run into similar "stuck" signals before on the S+ platform before.
One that is quite common is the "61-1 Loop".
However, even with all said, I still believe there is a wire crossed somewhere in your machine which is picking up wire signals that were originally intended for the candle or display panels' "Insert Coin" and "Coins Played" lamps.
Remember, the more you can describe and tell us - the better we can help you.
Pictures sometimes, can tell a million words as well.
Thank you.