That actually looks (and sounds) like "macro" vibration to me (rather than micro vibrations) that usually come from cables etc. Usually that means something big (like a bad motor) or less often one that is sevrely out of balance and could be balanced. Normally the wires touching cause the "micro" vibrations. Not always, but most often.
What "I" would do, is take a vibration analyser to it, to see where the vibrations are coming from. In this case, "I" might even hover the thing in front of me and gently feel for vibrations on each leg and arm, although that isn't for the faint of heart (or the slow). That would give you an idea where to start.
Have you had any crashes? If so, you might need to replace a motor, and you might even be able to see it. Look for dents and gashes...I have seen some motors (after crashes) that were so bad they couldn't be balanced. In that case, replace it. The bearings will go out on it anyway, and it is better/cheaper to do that on the ground.
In any case, I would aslo balance the motors. This is a thing I do instinctively (from decades with doing video and RC) but many people skip this. That is OK if you get lucky, but not if you don't. It can be more important than balancing props, as motors can be more out of whack. You can get lucky (and many people do) but it doesn't look like you did.
I now use an IOS app called Vibration to test for vibrations and balance. It is $5, and uses the accelerometers in the phone. You can use any vibration analyser, as long as you can start and stop it, keeping a "recording" over a period of time, and measure it against a set of numbers .
I use double sided tape on the back of my phone, to stick the phone to each arm of the Solo I also use soft foam blocks under the legs (pulled from other doodad boxes) to isolate the Solo from the bench.
Use this video as a guide.
I then use the motor test function of Mission Planner to run a set of motors up and down to see the midpoint area that has the worst vibration, and to test each motor indivisually, and to balance them. The speed you are looking for is where your motors are likely to be running when you are filming. Typically that is about 50%, and balancing Solo motors seems to work well there. I start the motor for 30 seconds and record it, noting the highest vibration. I also use metal tape, as it is heavier, and tends not to get soft when warm.
To connect Mission Planner, connect the PC to the Sololink network, and after that follow this guide to connect. You only need to change the connection type to UDP and connect.
I am not at the Solo right now, but at that point, I "believe" after connecting it, go to initial setup, and I "think" optional hardware, and then motor test. It could be somewhere slightly different, but close to that. In any case, there is a row of buttons,. The first 4 will be your motors Change the value to 50 and the duration to 30 seconds. and hit the buttons one at a time (1-4) to start each motor.
None of this is an an exact guide for Solo, but you should be able (as I was) to piece together what you need to balance the motors.
"I" would also take this opportunity to make a VERY close inspection of the Solo when the individual motors are running, feeling the motors, arms, legs, gimbal, camera, etc. for vibrations, and noting the worst, and how the vibrations are traveling. That is ultimately your problem. You can (as an example) swap motors, to verify that large vibrations go with the motors. I haven't seen it, but I have heard of people (on various copters) having "reasonant" vibrations on things like legs, where they act like tuning forks. In those cases, you can change the resonance by adding sorbothane. I have also seen people do this on GoPros and gimbals. I have done this on bike mounts etc.
In the end, if you think about it, Solo isn't really any different than any other multirotor in this regard. The gimbal will get rid of quite a bit, but can only do so much. It has four motors, and one or more of them is originally generating the problem, and then it is transmitting to the camera causing your problem. Obviously not all off them do it, so you know it "can" work, and your job is to find the vibration(s) find how itehya are transmitting. then get rid of them/it.
The tools above will help you find it/them. What you do to get rid of them depends on what you find/.
Good luck!!
PS: We might want to add this (or something like it) to the sticky guide. Or "maybe" an enterprising video person would want to make a Solo specific motor balancing video? Just a thought ")
