may be from where they did not seal the tree where they pruned it there in the pic or
sounds like to me you could have some type of tree borers, that is clearly a warning sign clear sap running is from something intruding the cambium layer. If it is a borer you better have them spray some
chlorpyrifos, linden or endusulfan to kill tree borers.
Spray the entire trunk and branches of the infested tree. Though the insecticides cannot reach the larvae that have already tunneled to the sapwood, they will kill all larvae and adults present on the bark surface.
then what I do is take a paper clip and dig as far as you can where the sap whole is in the bark and if you get lucky you will get the larvae.
then to prevent further attacks in the future paint the base of the tree with any type of latex paint preferably white, from about 18 inches up from the ground level of the trunk of the tree....let me know if you need any more help cause I hate them pesty things.............what they are is different kinds of moths that lay their eggs at the base of a tree, then all hell starts from there....