It appears when you go into an instance, the program needs to "re-get" XP bonus. When the character first enters the instance, it has its XP bonus form gears. However, it does not have the extra XP bonus such as from SH boon. It takes another 10 seconds to get the rest. If one invokes, submit quest before the 2nd portion of XP bonus registers in, those XP bonus will not be counted. Effectively, lose XP.
First, I thought it was just when I first login to the character. Now, I found out it is changed when you change instance.
e.g. When I login to the character, I have 70% XP bonus. I move the cursor to the bar and wait for N seconds, it switches to 130%.
I enter Workshop and check right the way, I have 70% XP bonus again. Need to wait for M seconds before it gets 130%.
Then, I left Workshop and go back to PE, I have only 70% XP bonus again. Need to wait for O seconds before it gets 130%.