We are a beach restaurant and have 2 x Crown CD1000' s powering 8 Bose 251 speakers. Purchased 2013, they worked great. This year 2014, after 6 - 7 hours playing, they both start to show red thermal lights even though they are not warm. The sound then compresses. This happens to both amps at more or less the same time. We use the amps the next morning and they are fine again until the same hour when the same thing happens. We do not change the volume throughout the day. The volume is low throughout the day, at about 15-20% of the output capability. During the problem, if we restart the amps we receive a 'lo line' message, then the amps start and the same thermal light/compression problem kicks in immediately. The amps are not outside, but are exposed to sea air. All signal issues arriving at the amps have been double checked. Shorting of speaker cables doesn't seem to be the problem. Any ideas?