Not only can the MACRS asset classification cause what you see, but so can reporting losses on some assets and gains on others.
If you sell at a gain, it's important to show a gain on all assets. Doesn't matter if the gain is $1 on some assets, and $100,000 on other assets. A gain is a gain, is a gain, is a....
When you show a gain on some assets and a loss on others, the depreciation is not correctly recaptured and taxed as ordinary income on those assets you show a loss on. Instead, that recaptured depreciation is included in the gain and taxed at the capital gains tax rate.
