Michael,
If you are using a blade type stabiliser, please check that the friction pads are in good condition and that the friction pads are tensioned to the correct torque (usually 27 NM or about 60 ftlbs)
You'll need to visit the web-site of your stabiliser manufacturer and download the simple servicing information for this job - but you will need a torque wrench to accurately set the tension
An AL-KO coupling head stabiliser is more convenient, but in general terms offers the same amount of stability improvement as a blade type (and the friction pad torque setting is automatic)
In the Bath University study on caravan stability, a stabiliser (blade or AL-KO type) was shown to offer a very significant level of stability, but how you load the caravan also has a significant effect on stability - heavy items low down, near the axle, etc.
Robert