Ok, I'll just try to educate, rather than blatantly say upgrade and give you some tips to at least reduce your ills.
First, print from SD card only when using the DC motor MK5 and trying to print extremely accurate. Trust me, it makes a difference no matter what other people say. There is physics and math behind the reason. It all revolves around max latency which is hard to measure or account for. Those curved ends tend to make this happen more, because a curve has more points in a given distance that must be transmitted.
Honestly, you can increase the flowrate or smash the layer, they both result in the same bonding action between layers. The flowrate to feerate is also basically a ratio, so changing either one does work too—although, we've all said run a DC motor wide open 255 and always use feerate speed to adjust actual thread width. The flowrate will change with a DC motor when PWM is less that 255 due to voltage sag when the heaters kick in. Also, it was for a long time locked out that the motor wouldn't even run below 255 in the firmware. Pretty much meaning your only choise is to slow down the feedrate (go at least 2mm/s slower than what you have now.) I find that the calibration cubes doen't help you get this right. Perfect fill (we look at the top surface normally) will actually cause poor bonding in tall walls. A slight overfill is actually where we want to me with any mechanical part, especially anything that need to be water tight.
I honsetly am no longer runnning any DC motors, so I cannot think of other tips.
