Error: found non-noded intersection between LINESTRING

[HeiKima]

Could you help me with this issue?
By computing the fragmentation step this error occurs:

[internal error] reportError : GEOS-processing error: Differenz gescheitert.. TopologyException: found non-noded intersection between LINESTRING (4.15488e+06 2.76965e+06, 4.15491e+06 2.76968e+06) and LINESTRING (4.15485e+06 2.76962e+06, 4.15491e+06 2.76968e+06) at 4154908.9316633195 2769675.1454799455

to mention: I processed the exact same operation but with a smaller buffer before and it worked. So the Question is, how can I dissolve intersecting buffers of two or more different (road) lanes, given as lines (not as polygons)

And also:
After I computed a first constellation, a second run doesn’t work. This error occurs:

[info] Setting extent CRS to ETRS89 / LAEA Europe
[info] Workspace directory set to '/Users/dosomething/Documents/MA/GIS_MA
[info] Outputs directory set to '/Users/dosomething/Documents/MA/GIS_MA
[info] Temporary directory set to '/Users/dosomething/Documents/MA/GIS_MA/tmp
[warn] No layer selected
[info] FragScape model saved into file '/Users/dosomething/Documents/MA/GIS_MA/2019_Frag_50015.xml'
[info] FragScape model saved into file '/Users/dosomething/Documents/MA/GIS_MA/2019_Frag_50015.xml'
[info] ******** BEGIN : Landuse classification
[info] Calling processing algorithm 'FragScape:prepareLanduse'
[internal error] reportError : Error: Algorithmen FragScape:prepareLanduse not found
[warn] Failed to call prepareLanduse : reportError : Error: Algorithmus FragScape:prepareLanduse not found

By saving the file and restarting QGIS the exact same operation works.

I am looking forward to your response.
LG
HK