There are several reasons why this could happen, here are some steps you can take to troubleshoot the problem:
However, merely using Bandaged BD has very little risk of causing you to get banned from Discord.
RIGHTS TO USE THE SERVICE
You agree not to (and not to attempt to) [...] (ii) copy, adapt, modify, prepare derivative works based upon, [...] or otherwise exploit the Service or any portion of the Service, except as expressly permitted in these Terms.
Betterdiscord is provided "as is", without warranty of any kind, express or implied, including but not limited to the warranties of merchantability, fitness for a particular purpose and noninfringement. In no event shall the authors or copyright holders be liable for any claim, damages or other liability, whether in an action of contract, tort or otherwise, arising from, out of or in connection with the software or the use or other dealings in the software.
While Bandaged BD does indeed violate the Discord Terms of Service, Discord has not been seen to take action on users for the mere usage of Bandaged BD.
Of the (estimated) over 20 thousand users of Bandaged BD there have been 0 known cases of Discord banning someone just for using it.
As long as you stick to plugins you obtained from the #official-plugin-repo channel in the BetterDiscord server you should be safe from being banned.
The latest statement made by a member of the Discord team matches what is stated in the Terms of Service regarding punishment.
The Company reserves the right to refuse any user access to the Services without notice for any reason, including but not limited to a violation of the Terms.
The statement essentially says that they reserve the right to choose whatever punishment they'd like, including no punishment, however saying that they will not punish ToS violators would be like saying they do not enforce their own rules.
Betterdiscord is provided "as is", without warranty of any kind, express or implied, including but not limited to the warranties of merchantability, fitness for a particular purpose and noninfringement. In no event shall the authors or copyright holders be liable for any claim, damages or other liability, whether in an action of contract, tort or otherwise, arising from, out of or in connection with the software or the use or other dealings in the software.
Discord updates regularly change things that can wind up breaking themes or plugins.
Try reinstalling whatever is broken, and if that doesn't help complain to whoever made it.
There are a couple theme generators that allow you to make your own custom theme:
This one by Gibbu,
and this one by Spectra.
The first time BBD loads it downloads some emote data.
This will take 2-8 minutes to finish so just be patient.
If you want to prevent Bandaged BD from ever downloding new emote data you can disable the Download Emotes option in User Settings -> [Bandaged BD] Bandages.