When the helicopter is flying a circle without input from the transmitter and without changing the direction of the cockpit, you experience the so-called “Toilet bowl effect”.
This spinning is caused by problems with the flybar or the upper rotorhead or the joints which connect the upper blades with the flybar.
The flybar should move free without any resistance. If experience the TBE you have to check flybar and joints and the blades. If there are any ridges on the balls of the rotor head or the joints, you have to remove them. Silicone Oil is no mistake. But stay away from petroleum-based lubricants, they will attract dirt and then block the joints (and you will experience an increased TBE).
In rare cases the blades of the upper rotor are either fixed or screwed on loosely. This will cause vibration and sometimes also the TBE.
Worst case is a damaged shaft. Replace a crooked rotor shaft.