I’m working on lots of v8.2 instances and this issue was one of the most annoying issues I experienced.
You want to create or update custom entity (it’s not a problem on OOB ones) with custom value in one of the custom lookup fields. CRM REST Builder will always be my tool number one when it comes to creating Web API requests on Dynamics, but if you try it on v8.2 for the upper…
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Web API v8.2 – Bad request when setting lookup
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