Thank you for reaching out to us.
In regards to your first question, it seems you need to increase the allowed memory size for your WordPress installation. Please have a look at this guide to help you to increase this size:
About the second question, this might be caused by a conflicting plugin. I would recommend you to do a plugin compatibility test by deactivating all additional plugins. Then, check if this error persists. If not, kindly activate plugins one by one to see which plugin is causing this.
Please let me know how you go.