It still may be a faulty DC-In jack.
The centre pin in the socket may be loose and touching something when the plug is being moved.
I would have thought that uBreakiFix would have tested for this though, but you never know.
Fortunately it seems that the DC-In jack is not soldered onto the board for some Acer 5750 models, hopefully yours is one of them, but is actually a separate module that can be unplugged from the motherboard.
Here’s a video that shows how to remove the DC-In jack from an Acer 5750 laptop. View from about 7:00 minutes into the video to see the removal process.
If you decide to test the DC-In socket don’t forget to remove the main battery from the laptop, before doing anything else to the laptop so as to forestall any electrical problems from occurring due to tools slipping etc., physical damage to the components is a different matter ;-). Even though the laptop is off there is still power available at various point on the motherboard, until the battery is disconnected. The power button is not a power isolating button. Basically when off, the laptop is in what could be termed an extremely low power standby state.
Once you have disconnected the DC-In jack cable from the motherboard, use an Ohmmeter to test the connection from the centre pin of the socket to the appropriate (red) cable plug connector, to see if it is a solid connection, maybe loose or shorting out to the outer barrel connector of the socket. If it is determined that there is a problem in the socket, it cannot be repaired, it has to be replaced
Also if you have Win 10 installed, create a Win 10 battery report to check the condition of the battery just to see if it is still good or whether it is deteriorating