Reliability of Grove Modules

Hello, I purchased hundreds of Grove modules but I am just starting to use them on projects. I am using 10 Grove modules on WioLink computers and have found that both the Grove Recorder and Grove uv sensor are unreliable. On the uv sensor the readings are jumping all over the place (see photo below) and when I touch the cable next to the JST 2mm connectors the readings seem to settle down. Similarly with the Grove recorder - it works some of the time when I touch the cable near the connectors. Has anyone else had reliability issues with Grove modules? There may be a design issue - that is manually inserting the cables in the modules may weaken the solder joints connected to the printed circuit boards? Another issue is the lack of response from the Grove moderators. I was interested in the accuracy of the uv sensor and noticed that a similar request was posted almost three years ago with a reply by the moderator that promised to get back with an answer but failed to do so. While initially I was quite impressed with Grove I now have my concerns.
uv sensor gauge.JPG