I’ve had this problem since new and it has gotten worse. Prints flat objects OK but does very poorly when I print tall objects, especially RC plane wings. There are random areas with very poor line adhesion and little to no flow. Some are so bad you can see through the print surface. I’ve adjusted the filament driver several times, I’ve changed nozzles, I’ve varied the temp. All to no avail. How can I fix this? Thanks in advance.
If there is a picture, it might be better to understand and know what is the problem 
As you can see, there are areas where there is almost no material. The other side of this wing section printed well.
I had a lithograph do this on my sv01 pro. Prints fine flat but vertical it has missing sections. In the lithograph settings I was printing the thinnest layer at .4 and nothing would show up so I changed that to .6 And it seems to be working now.
Are you using the Sovol themed cura? What are your wall settings? I use 3 walls for nearly all of my prints so that’s 1.2 for my .4 nozzle. And for stronger prints I go as high as 6 for 2.4 wall thickness. I think Sovol cura defaults to something like .8 for wall thickness which isn’t nearly enough.
I recently had an issue that produced similar results. I was able to fix it by increasing the extruder tension and by making it easier for the extruder to pull the filament off the spool.
also, each of the Sovol printers I have received with the extruder tension screw is just barely screwed in and requires significant tightening. I inserted the filament and tightened until I can just pull back the lever and pull the filament out and so far that has been good.
I’m experiencing the same problem. I’ve already adjusted the extruder tension to the maximum, but it hasn’t resolved the issue. As you can see, the tension screw is set to the maximum. The problem occurs during the initial wall layer printing, and it appears that the extruder needs to accelerate the extrusion rate. Additionally, I’ve reduced the retraction parameter to 0.5mm. Once the wall printing begins, the flow stabilizes, and the wall is printed correctly.