CTP Screen PT-R8000 Expoure head error

Hello, i have a strange problem here.

CTP Screen PT-R8000 shows Expoure head error: Excessive current in the LD drive 1 (sometimes drive 2, very rare drive 3 and 4) while burning a plate.
This is old problem, from the moment we bought machine (about 5 years), but until recently it happens about 1 time in month/two months, and now error appears on every first/second plate.
Now we writing plates on half of head (0-15 LD), it's helps, but even so error sometimes appears.

What we do:
1. Changed cables and connector X800 (-5v, 8 black and blue cords from PSU to laser head motherboard).
2. Changed cables X807 (two cables from PSU to laser head motherboard).
3. Soldered all connectors on cpuboard and motherboard.
4. Changed pair LD who behaved strangely (sometimes show 1 mA in Iop-Iopd menu).
5. Many times dismantled head, pulled out and inspected all the boards.
5. Measured voltage in all PSU's, everything as reference values.
6. Raised voltage on head PSU to 5.43 (maximum value in service manual).
7. Connected oscilloscope to head PSU to measure interference - everything is fine.
8. Changed the power value of the laser head (270-260-250-240 mw, now working in 260 mw.
9. Observed the work of the machine via RS232 terminal (i can attach logs, but there is nothing interesting in them, just message about error).

At this moment machine works at full head, after procedure of opening-closing head cover, sometimes that helps burn up to 100 plates, sometimes not.

I think problem in some contacts, but in which?

Also we talk with service engineers, but they dont did not tell us anything new.

Maybe someone faced such a problem? Search in forum shows only problems with dead LD and broken cable.

P. S.: Sorry for a weird structure of proposals, english is not my native language.
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Hi Benjamin i have a similar problem in a PT-R8000 (JAVELIN) Im tryed to solve the problem with many of solutions that you post, but until now nothing works... a man techcnician gave me a tip "could be a CPU BOARD or Drive BOARD".

In my experience I tryed Changing the Drive Board (used) whitout results.

I am try to adquire a CPU board and Another Drive Board for try.

I hope the tips help you..

Keep me in touch about you, Regards
One of these days we will try reconnect (get out of the connector and insert back) all LD in head, maybe problem in some contact (somewhere there was such a case).
However, I doubt that this will help, most likely the problem is really in cpu or driver board, maybe invisible crack or something else.
Also it makes sense to swap driverboards (1 to 2, 2 to 1), maybe it clarify the situation.
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Ok, we reconnect 8 lasers from 32, and nothing happened.
Also now error arises on half head (0-15) channels, about once on 8 plates.
We think do not waste time and money on this machine now, and just will buy another CTP, and we will leave this machine as a spare option (and for the sake of experiments), but if there will be ideas about fixing that problem, i will keep you informed.

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