There should NOT be any caulking used for a roof top A/C Unit
A/C Unit is sealed using a roof gasket.
Evap Coil is under a 'sealed' cover under the shroud.
Drip pan has drain holes...if plugged condensation can overflow form drip pan and/or get pulled over by fan wheel
A/C Unit hold down bolts are loose.
Remove ceiling grill cover....in each corner will be a small bolt head. They hold A/C Unit on roof. They can vibrate loose so that roof gasket isn't compressed
Tighten them but just SNUG.....too tight and you will crush roof gasket/warp it and then it would seal properly either
Too loose/too tight----makes roof leaks possible