Based on the data provided, the following are potential root causes for the performance issues in the process:

1. Repeated rejections and resubmissions: There are multiple instances where declarations are rejected by various stakeholders (ADMINISTRATION, SUPERVISOR, BUDGET OWNER, PRE_APPROVER) and then resubmitted by the employee. These rejections and resubmissions cause delays and increase the time taken for the process to complete. For example, the process variant with frequency 36 has the highest performance time of 2542497.917.

2. Involvement of multiple approvers: Some process variants involve multiple levels of approval (e.g., ADMINISTRATION, BUDGET OWNER, SUPERVISOR) before the final approval. This can also contribute to delays and increase the performance time. For instance, the process variant with frequency 2473 has a performance time of 1084338.407, which is higher than the variant with frequency 1392 (performance time 854633.975), despite having a similar number of steps, possibly due to the additional approval step by the BUDGET OWNER.

3. Missing information: There are instances where declarations are rejected due to missing information. For example, the process variant with frequency 40 involves a declaration being rejected by MISSING, which then needs to be resubmitted, causing a delay.

4. Variation in approval times: The performance times vary significantly across different process variants, even for those with similar steps. This could indicate inconsistencies in the approval times by different stakeholders, leading to bottlenecks in the process.

To improve the process performance, potential solutions could include streamlining the approval process, reducing the number of rejections through better communication and training, and ensuring that all necessary information is provided with the initial submission.