rb2011-uias cpu spikes on routing process

hello, i have a strange problem on a rb2011 and some other 2011, my setup is ospf with loopback and 2500 routes, mpls enable and vpls. all its working as expected except that sometimes the rb 2011 routing process spikes ti 100% and 1 or 2 packet timeout. is i disable ldp/mpls all return to normal. i have summarized ospf routes from 3600 to 2500 and seems it works better, but i don’t understand how i can resolve this issue. the release is 6.34.6.

Thanks a lot for your help.

BR