The new MT190 tripods have a quick snap lock lever. The procedure is the same whether you have a 3 leg section or 4 section tripod. For this you will need an 8mm socket nut driver.
On the back of the leg lock is a screw that adjusts the tension on the snap lever. If it is really loose you may need to turn it a lot, generally you will only need to turn it a little bit. In my experience never more than a third of a turn. Unlock the snap lever, turn the nut driver about a quarter to a third of a turn and snap the lever tight. Check the tension of the leg. If it is still slipping un snap the lever and adjust it again.
Be VERY careful that you do not over tighten the screw. Short term you may not see any difference, other than it is very hard to snap. long term you will wear out and damage the snap lever and maybe even crack the leg lock. Carbon fiber tubes are very strong, in length, but not diametric compression. Too much pressure and you can crack and split the tube. A simple repair then becomes a much more expensive leg tube replacement.
If you are having problems, or for a tune up or for repairs, send your name, address, daytime phone and email address along with your tripod to:
108 Garner Road
Spartanburg, SC 29303
Once we have it, we will evaluate it and contact you. Please send us your daytime phone so we can reach you during business hours.
Lastly, if we are repairing your Manfrotto Product; we are recycling all broken parts and scrap articles. Almost nothing goes into the trash if we can help it.