GPU fan speeding up every other second

Hello.
A couple days ago my desktop computer's graphics card's fan started acting up. I'm currently using Asus' GTX 750 Ti with a brushless single fan manufactured by Firstdo. When I use my computer with a low gpu load (e.g. idle or browsing the internet with chrome while skype and other everyday programs are running as usual) the fan doesn't spin at all except when it randomly every other second speeds up for a very short while and makes a lot of noise while doing that. When playing games where the gpu load usually rises above normal everyday usage, the fan will spin with a low and silent speed but still occasionally speed up for a couple seconds.
So far I have cleaned the whole computer of all possible accumulated dust, uninstalled and reinstalled my graphics driver as well as oiled the fan in question yet the same problem persists. Is there anything else I could do to troubleshoot/fix this or should I just go and get a new cooler for the graphics card?
 
Should probably have mentioned that I have tried controlling the fan speed manually. Interestingly whenever I set the speed to less than approximately 80% of the maximum speed, it will constantly slow down before picking up the pace again. The noise made by the fan is still very annoying and way louder than it used to be.
 
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