Japanese Maple - Dying Branches

[Kim_JP]

Hello!
I have had my maple bonsai for about three years now. Recently, several of the main branches have started to dry out and die. This often begins near the leaves, which turn brown, and then the entire branch dies within a couple of days.
I regularly water the plant and keep it out of direct sunlight during the summer. (Two years ago, all the leaves died after just one day of direct sunlight.) The leaves fall naturally, and I have not pruned it myself.
What could be the root cause of my recurring branch loss?
Any advice would be appreciated!

 

[Shibui]

Seasons are often important for bonsai related questions. looks like new growth on the tree so I'm assuming you are somewhere in Southern hemisphere. Adding a general location to your profile saves us from asking each time you post.

Looks like a fungal infection which is not uncommon for JM. The whole tree looks unhealthy. Not sure if that's related to the light levels, nutrient deficiency or root problems or a combination.

Indirect light is OK and can protect from sunburn but trees do need a certain amount of light to make food. Not enough and they decline. I would try for a bit more sun and adjust watering to cope with the extra sun. With good care a JM should be able to cope with 1/2 day sunlight - depending on where in the world you are and how intense your sun gets.
No mention of fertiliser regime. All the watering we do to keep trees in small pots alive quickly leaches all available nutrients out of the pots. Most of us apply fertiliser every 2-4 weeks to maintain nutrients and tree health.
I can see the pot is on a wire stand which is a good start to drainage but watering too often can keep the soil soggy leading to root rot. I've found that akadama stays wet longer than most potting soils. Conversely, soil getting too dry can also damage roots leading to dieback too.