PS4 controller on charge, blinking red

So my controller had stopped charging for a while, regardless of what I did to set it up. I sent it off for repair, and recently got it back. The upside is that it seems to be responding to the charging, but the downside is that it doesn't flash orange, it flashes red.

It occasionally will flash orange, but it will only do that for a few minutes when I first connection to a power source, before going red again.

Edit: after a bit more testing, regardless of how long I connect it to a charging source, when I disconnect it, I get a low battery notification, and it quickly disconnects. I am also yet to find anything about the blinking red light.

I was unable to find any hard evidence as to what the problem was, or what the blinking light meant, or if it was even meant to be doing that. However, after sending it back in for repairs a second time, the problems was resolved, after a full "repair and clean" was done. The controller was fully cleaned, the internal battery replaced, and the connection point(s) once again properly configured to connect correctly.

Some potential causes might be:

• The port/battery was again, not properly connected.
• The battery was too old to hold charge.
• Dirt/grime was affecting the connectivity of the port/battery.

The light simply might have been a mixture between the "charge light" (slow blinking) and the "low battery" light (red colour), though this issue is very unique - no evidence of this problem has been found before now.