Mine does the exact same thing and has been since the first day I got it. It also likes to crash for obvious reasons with any decent overclock when it hits 1.3. I turned on LLC level 3 in the bios, on the advice of another member, and at 1.35 manual that actually runs it between 1.33 and 1.37 according to cpu-z. I saw it actually dip back to 1.3 even with that on, but only for a fraction of a second over a long period of time. Although I'm not 100% sure how accurate cpu-z readings are this mobo. I thought I had read somewhere that it wasn't.
So I moved up to LLC level 4, and dropped voltage to 1.34. This ended up giving me the 1.352v I was looking for under 100% load. It still drops to 1.33v, but only at idle, which is fine. Also make sure you disable core boost, core boost was cranking up the base clock to 115 sporadically and the cpu was jumping well over 4GHz. I can't get this 1700 to run more than 3.5GHz across all cores on this bios. I was pushing 3.7 stable and a slightly less stable 3.9 on the last public bios release without doing anything. I'm really scared to do much at this point, every time I adjust the multiplier the cpu temp no longer reads, so i have no idea how hot this thing is running under a wraith cooler.