It sounds to me like some users do not have the "Current" clip selected, which could definitely yield these results. I recommend using the Color workspace because it enables "Selection follows playhead" which will ensure that you always have the clip under the playhead selected.
As a recap, these are the steps to successfully use Color Match
- Enter the Color Workspace
- Park the playhead on the clip that needs some color correction (it should get automatically selected)
- Enter comparison view mode by clicking the comparison view button in the program monitor button bar or in the Color Wheel & Match section
- Select the reference clip on the left by using the scrubber, the arrows or the timecode under the reference side. This has access to the entire timeline.
- Click on the apply match button in the Color Wheels & Match section.
- This will match the current clip to the reference by altering the color wheels
- Exit comparison view by clicking on the comparison view button in either location
Pro Tip: If the shots are incredibly different, like the exposure is wildly different, it helps to get them into the ballpark first with basic corrections. The color wheels can only do so much, but Color Match is smart enough to take into account any corrections done upstream of the Color Wheels when calculating the match. If you run a match and it pegs any of the color wheels parameters, it means the shots are too different, and the color wheels don't have enough latitude to make the match.