Waterman and the converter

This converter is to be suitable for all fountain pens by Waterman. This eliminates the need for the continuous purchase of ink cartridges that also in Germany are much more expensive than in the country of France. Therefore, it is recommended that an inkwell to buy from which the converter can be refilled many times. The cartridge pen is thus quasi retrofitted to piston filler. So far so good. I own two purchased from various vendors Converter Waterman, both identical, that does not serve its purpose, as they provide no sufficient ink flow. I have the converters used in different models (MAN 200, Expert, Phileas) and always had the same problem. The ink flow set out again, especially with fast movements with the pen. The typeface is uneven and the spring begins to scratch.
When inserting a cartridge turned immediately back on a normal ink flow. Why this problem occurs, is beyond me, I am familiar with fountain pens from good and therefore does not believe that I'm doing something wrong when filling. In this respect, I can recommend the converter from Waterman limited. Does anyone have similar experiences?