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While printing, when the flowrate is reduced via Repetier-Host OR the printer's LCD screen, the extruder runs at the slower rate until it reaches the end of a line. At the end of every line, the extruder quickly accelerates and dumps excess plastic (very evident during infill direction reversals), then continues the next line at the slower rate. The longer the line, the greater the dump at the end of it. Flowrate adjustment works in MatterControl, yet I still prefer Repetier Host. I posted this on the repetier forum http://forum.repetier.com/discussion/15 ... ion#latest and they suggest a firmware upgrade to 0.92.8. Before I attempt that, I'm checking here to see if this is a known issue with an easier fix, as I have not been able to find any.

Printer: Rostock Max V1 April 2013
Board: Rambo 1.1b
Repetier Host 1.6.0
Firmware: 0.91S by SeeMeCNC uploaded via Arduino IDE 1.6.1 with Arduino Mega 2560 board selected. Configuration.h and pins.h modified for a 2nd extruder/hotend but is currently not used - number of extruders set to 1.
Extruders: DGlass3D HPX2 2:1 ratio with "half-sized" NEMA17 steppers, tuned to 498 steps/mm

Extruder config values:
Start feedrate 45 mm/s
Max feedrate 100 mm/s
Accel 6500 mm/s^2

Which slicer are you using? I've had something similar, and I believe it is related to the extrusion distances being in relative or absolute mode. I can't remember which causes the behavior, but I want to say that using absolute extrusion will prevent this problem, while using relative extrusion will cause this problem. This is just a guess, as I simply quit adjusting the flowrate on the fly and adjust it via slicing now.

Slic3r. "Use relative E distances" has been off. I'll try it next print.

Did this change anything with the behaviour?

I decided to just upgrade the firmware to 0.92.8 for multiple reasons - extrusion flowrate adjustment now works in absolute distance mode. There are also new additional high frequency pitches during XYZ stepper operation ( I suspect due to algorithm improvement?) that make the printer sound "drunk" lol.