Trees rise out of the pot for 2 reasons:
1. The soil washes away from the roots. Obviously the trees is not actually rising in this case but looks like it is.
2. Roots grow in the pot, especially in layers at the bottom of the pot. Successive root growth pushes the tree higher in the pot. Cure: repotting and root pruning ( at the appropriate time of year) to remove the layers of roots.
This happens sooner or later to almost all trees in pots. Quicker in small pots and quicker if the tree grows well.
I had a small trident that grew vigorously every year and pushed itself up out of the pot every autumn.
Tying the tree into the pot tightly can help stop it lifting itself out.
Agree that your trident does not look too good. Looks like screen mesh behind the tree. Hope it is kept outdoors?
Brown leaves on maples can be from a range of different causes.
Most likely is not enough water and/or dry winds are burning the leaves. Increase shade or increase water, esp on hot days.
Conversely, too much water can also cause damage to roots which then means the remaining healthy roots can't supply enough water, even though the soil is saturated.
High mineral water or saline water can also burn leaves by preventing water getting into roots. Minerals can slowly build up in the soil if you don't flush lots of water through the soil occasionally.
Not enough light and air movement can cause slow decline and eventual leaf drop. That happens to many trees kept indoors.
