Why chance all the bearing if just one is the "issue"?
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Since the camshaft is one piece, it is good practice to change all of them at the same time. I have never heard of just one being replaced. If the other used ones reach the wear limits faster than the new bearing, then you could have the same situation in a different spot on the camshaft.
On that type of cam bearing, I have only done engine out of vehicle cam and bearing replacements.
From personal experience, once you have it opened up, the cam out, with the proper cam bearing tools, not that much more to replace all of them. I do not know about this engine, but whenever I bought cam bearings, you had to buy a complete set - could not buy just one.
When doing crankshaft, always replaced all main bearings, when doing double overhead cam engines, which have split bearing inserts and bearing caps, always replaced all the bearings. Just say'in.