I don't understand why do you think soap with a pH of 10 is bad -- why does that need to be fixed? And why are you basing your concern on just a pH measurement?
Lye-based soap with no excess lye and no excess fat should have a pH somewhere between about 9 and 11.5 depending on the fatty acids in the soap. Assuming you measured the pH accurately, 10 is within that typical range.
You cannot know if the soap has excess lye based on pH alone, by the way. Again, depending on the fatty acids in the soap, one soap at pH 10 could be fine -- no excess alkali -- and another with different fatty acids could be lye heavy.
As far as the lye flakes, you really haven't given us enough information to troubleshoot. Give the actual recipe you used for the soap (all ingredients all in weights). Describe the method you used to make the soap. Have you used this exact recipe and method for previous batches or did you change either, even slightly, for this batch.
A picture of the soap would also be very helpful.
Also explain how you made the lye solution. Did it sit in the open air? Are you using different NaOH than in the past? Was the lye solution stored for awhile? If stored, how do you store it? Did you make it with distilled water, tap water, or another liquid?