This is likely, due to conflicting setting within your bot.
The setting in question, is the chan-mode channel setting (.chaninfo and .chanset).
Many people get confused at what this setting does, and how you go about making changes to it.
It is used, to set what flags should be enforced (not set) in the channel.
IE:
using +nt will make sure the channel is set +nt at all times, yet allow all other flags to be set and unset freely.
using +nt-l will make sure the channel is set +nt at all time, and will refuse to allow the +l flag to be set.
Using this system, you should see where your problem lies.
the chamode setting is designed to tell eggdrop what it should, and shouldn't be setting/enforcing on the channel. All other setting are ignored.
EG.
"+t" = Make sure the channel is +t. If not, set it, if changed, change it back.
"-t" = Make sure the channel is -t. If set, unset it, if changed, change it back.
"" = Ignore all changes. No matter what you change, eggdrop doesn't care, as this is what you told it to enforce.