There is an existing hotfix Hfix-22332 which resolves this behavior. There is an additional instruction that needs to be followed. After installing the hotfix, if the Field Values already contain encoded values then manually replace them with & and Resave the field values.
I have raised an SR , they have provided the HotFix(HFIX-22647), but the problem is after installing that i need to check all the field values and save it, which in my case is around 12,000 records including few pega defined. I am also trying another approach if it fails, i may install hotfix and let you know how the process went.
New Update: There are few issues with the HotFix. If you can solve using replaceall or with some other function it makes your work more easy.Or conside like & is causing issue then you can go for and instead of it. If there is no option go for this Hot Fix, and then need to check your application completely from end to end wherever you are using field values( as here my resolves around it)