The Singularity is approaching (my printer has a mind of it's own)

[Halphinian 0]

My printer has had some problems recently, and I finally got around to fix them a couple of days ago. Once the repairs were made, I tested it on a couple of small parts and it was satisfactory. I was proud of myself, so I decided to print a couple of larger parts. Here are the results:

These were the first small parts that I printed after the repairs. As you can see, the printer lines are slightly visible, but it is smooth to the touch and I like that textured look anyway.

These are the larger prints that weren't so successful. As you can see, the ribs on the inside of the part are mangled. The only way I can see to fix this problem is to slow the print speed. This is my second problem. My printer does not want to listen to me anymore. When I printed the first part, it was on the default speed on Cura 15.04 (I think it's 50) and it printed ok, but I decreased the speed to 35 because the other small part was more detailed. It began printing, but it was still printing at default speed. I was distracted because the part came out nicely, so I ignored the issue until I began printing the larger parts. The first large part was flawed, so I decreased the print speed to 25 and started up another part. The printer kept printing at the default speed. I have tried using different computers, speeds, parts, and every single time it prints at the default speed instead of the speed I inputted. All of the other variables function properly (nozzle temp., bed temp, fan speed) except for the print speed. I have no idea how to solve this problem and hope it won't result in having to buy another printer. Please help me reason with my insubordinate printer and restore peace between us.

I used a Surface Pro 3 and an Ultimaker Original Plus with Cura 15.04. If I can figure out how, I will also provide the files that I printed

PLEASE HELP!

[nallath 1,101]

How does the fillament look? Is it mangled / digging into it? I've had it more often that smaller prints would work because then there isn't enough time for the feeder to fail (the pressure of previous layers would finish the top ones). The large objects would then fail as it would not have enough pressure.