No Bug. Vote power increased with a factor of 4, meaning your current 25% vote power on the slider was the old 100%. With the new 100% you can vote about 10x a day to kind a keep your vote strength. Around 50 full power votes wil bring your vote strength to zero.

Also the vote itself is now liniar, before it was the square of, ie large SP holder having MUCH more power over small SP holder.