weird issue with vsync

[nvious5733]

Hi,

currently I'm having weird problem with vsync fps seems to be locked below the monitor refresh rate all the time for example while playing battlefront without vsync on i consistantly getting 70 - 80 fps all the time but with vsync on it's drop my fps to 38-40 which is very weird to me  also Witcher 3 also suffer the same problem I edited setting file to cap fps at 32 while having vsync on and few weeks earlier with this setting I was able to get 32 fps almost locked all the time but now suddenly this week with vsync on fps keep getting drop to 28 and below.... what could be the issue here? I tried google it but haven't seen anyone coming across similar issue before  

btw my spec is as follow 

cpu : i7 6700(non-k) stock clock

gpu: galax 1070 exoc also at stock clock

ram 16 gb ddr4 

mainboard:gigabyte B150M-HD3 

PSU:superflower 600watt

 

[nvious5733]

ps. prior to today these two games was running steady with vsync on with witcher locked at 32 fps and battlefront at 60fps