They say the pullback in U.S. equities may be more than just a passing phase.
Both firms cited the U.S. elections as the key source of uncertainty for markets ahead.
Low liquidity can leave stock markets particularly vulnerable to exaggerated moves around big options trades.
Bulls say there are plenty of good reasons why technology shares can be supported at current levels.
Investors have been placing election-related bets earlier than usual given a polarized political climate.
The impact on public opinion of violence around protests, as well as potential poll bias, gives Trump momentum.
A gauge of sentiment from the American Association of Individual Investors is also in bearish territory.
Among the reasons for optimism is doubt over valuation measurements.
The relationship between equities and fixed income has broken down.
Portfolios that overweight government bonds will return as much as 20% over the next year, this firm says.